“I’ve lived many years in Kentucky.”

Despite being an inveterate pedant I have no issues with that format.

More grist:
1) "He searched five years for his estranged daughter."
2) "He sought five years his estranged daughter."
3) "I was two years buiding a trimaran."
4) "Seven years I studied Latin."
5) "i was two hours waiting for the ambulance"

Part 1 - For the original question: it seems neither particularly American, nor particularly new:

"and he lived many years there, after my return to England."
The Valetudinarians Bath Guide, London 1780

The next two aren't exactly the same pattern, but do omit 'for':

"Hildanus relates the case of a girl who lived many years without food or drink"
Encyclopædia Metropolitana, London 1845

"Olympidorus the platonist, assures us that he knew a person who lived many years, and in his own life neither fed nor slept, but stood only in the sun to refresh himself."
The Mirror of Literature, Amusement, and Instruction, London 1841

Part 2 - More grist

1) "He searched five years for his estranged daughter."

As well as the adverbial cropping up in an unexpected place, there's the added problem that 'searched' and its dependent preposition 'for' have got separated. I'd never say it myself, but there are a few examples of this type do exist at Goggle Books, although in infintissimal numbers (from Ngram "searched * years").

"In a foretaste of what was to come, the symphony board searched two years for a new music director to succeed Alessandro" - Texas Monthly 1987

2) "He sought five years his estranged daughter."

Absolutely no way! This sounds like Google Translate - you seek somebody or something. All the examples of "sought * years" I've found at Ngram turn out to be red herrings, such as - "which he sought five years ago"

3) "I was two years buiding a trimaran."

Wouldn't say it myself, but ...

"Solomon was seven years building the Temple" from perhaps 1814, and reproduced several times in the nineteenth century. This is the only example I can find at Ngram of "was * years building". There were no results at Ngram for "studying, making, doing", or example.

4) "Seven years I studied Latin."

No problem in the right context - "Seven years I studied Latin, and what good did it ever do me!" This is classic fronting for special effect.

5) "I was two hours waiting for the ambulance"

At first sight, it doesn't seem too bad to me, in informal conversation. It hasn't separated "waiting" and "for", and the shift from normal word order seems to stress the two hours (but see below). However*, in the whole web "I was two hours waiting" gets precisely 4 hits, and one of them is this post. Of the others, one is Russian, one Portuguese, and this one from New Zealand - "Yesterday I was two hours waiting for my appointment with a specialist." (and he turns out to be originally from South America). And in case you think I'm being too restrictive, here are a few others: "one hour" - 1 hit, "an hour" - 3 hits, "three hours" - 0 hits, "four hours" - 0 hits. So probably best avoided.

*Michael Gove, British minister of justice, has written to his department suggesting that they don't use "however" at the beginning of a sentence. I was taught the same at school, but have no idea why. As far as I remember nobody mentioned doing this with other conjunctive adverbs, such as "nevertheless, consequently, accordingly, moreover" etc. What's so special about "however" I wonder.

One alternative in (1) and (5) might be to use a bit of fronting:

"Five years he searched for his estranged daughter, but to no avail."
"Two hours I was waiting for the ambulance, and nobody even bothered to call me to say it was on its way!"

@WW Thanks - I found this topic difficult to google. It does seem that we can sometimes drop "for" with time-duration expressions where the meaning is clear from the word-order.

Re "however": this no longer appears in the latest Strunk and Cowan online. Indeed it includes:
"However, the distinction is often fine and sometimes invisible."

For IELTS purposes, instead of "however", I usually tell my students to think about using "although" or "whereas" , and joining up with the foregoing sentence. (The marking criteria include: "uses a variety of complex structures".)

To me, there are two special things about "however" vis-a-vis other adverbs such as "admittedly" or "nevertheless":
1) "however" tends to mark the foregoing word as the item of contrast.
2) "however" is more readily mobile in terms of position.
Consider:
a) However, he was very young.
b) He was, however, very young.
c) He, however, was very young.
d) He was very young, however.

I teach people to use commas here off because the examiner may have been raised on Strunk, and I sometimes question the use of "however" at the beginning of a paragraph, as it so often betokens lack of topic cohesion withing each paragraph.

I know many Americans were raised on Strunk , but the book is is almost unknown in the UK. What's more his chapter on the passive is so awful I wouldn't be likely to pay any attention to anything he said anyway - he gives four examples of "weak" passive sentences, only one of which is in the passive. And to prove how much better the active is he compares these two sentences:

"My first visit to Boston will always be remembered by me."
"I will always remember my first trip to Boston."

Only thing is that not even the keenest fan of the passive would ever utter a ssentence like that. We rarely use pronouns as agents, and especially not "me". It's strange how passive-bashers always like to use these "by" comparisons, even though 80% of passives don't have an agent.

I do see what you mean, though, about the flexibility of "however". Sometimes it is better after the subject or the verb. However, that's not always the case. And the use of commas here is surely universal, whether or not the examiner has ever heard of Strunk, just as with any other conjunctive adverb.

@WW utterly agree with you re passive. One would hope the examiners do too.

IELTS marking scheme does mention "good control over punctuation". What exactly they mean by this - especially comma usage - is not specified, but I presume pretty old-school.

I guess an "inveterate pedant"might insist on commas in the following:

"He was admittedly very young."

"I will give you a call if I have time."

@jayles - I don't think even an inveterate pedant would have any grounds for insisting on commas in the second one. As far as I know, the accepted (and traditional) rule is that when the subordinate clause comes first, we use a comma - "If I have time, I will give you a call", but when the main clause comes first, we don't use a comma, or to put it another way, we don't use a comma when the main clause comes first.

Your second one I'm not so sure about. If admittedly had come at the beginning of the sentence, yes convention would suggest a comma. But used as in your example, commas seem rather to be optional. In the first twenty entries of "was admittedly" at Google Books, only two use commas, and the picture's much the same if you restrict the search to the 19th century, which are mainly from official or legal reports, but also include comma-less versions in literary magazines, etc. So you can find both in legal reports:

"nothing turned upon the notice, and it was, admittedly, binding upon both the landlord end the tenant." 1826

"That case is deserving of some notice, for the contract there was admittedly binding between the parties" 1847

and comma-less versions in more literary magazines:

"First, as to the sanity of her mind, or rather as to the extent of that one delusion, for she was admittedly sound upon all other subjects." The Annual Register, 1839

It's not that old a word, apparently first appearing in 1780 (it's not in Johnson).

@WW Thanks for your research.

Whilst commas are generally used to show how the sentence is to be read, there are some disparate views on the detail:

1) British vs American usage - see:
http://www.gsbe.co.uk/grammar-commas-and-full-stops.html

2) "But with the current fashion of minimal punctuation, [commas] are now often omitted" - ibid

3) The use of the "Oxford comma".

Sometimes the "rules" seem too dogmatic or restricted in scope:
"It is not usually necessary or indeed correct to use a comma with the conjunction 'because'."
http://www.bristol.ac.uk/arts/exercises/grammar/grammar_tutorial/page_06.htm

Perhaps one's ideas about what is right or wrong just depend on which university and whatever rules they apply.

@jayles - I agree with point no 2 when it comes to two indepent clauses, but strangely neither of your sources seem to specifically mention dependent clauses. However I think the principle outlined above is fairly well standard. It's taught in British English course books, for instance when talking about conditionals, and on American university websites. This is pretty typical, from Towson University:

"Comma use with adverbial clauses depends upon placement of the adverbial clause. If the adverbial clause introduces the sentence, place a comma between it and the main clause. If the adverbial clause follows the main clause in a sentence, do not place a comma between the two."

http://www.towson.edu/ows/advadjnomclause.htm

And this from DailyWritingTips:

"The simple rule is this: If a subordinate clause precedes the main clause, separate the two with a comma:

Unless you have a lot of money, steer clear of Rodeo Drive.

If the subordinate clause follows the main clause, no comma is usually needed:

Steer clear of Rodeo Drive unless you have a lot of money."

http://www.dailywritingtips.com/subordinate-clauses-and-commas/

But no doubt there are always exceptions. This rule, I think, makes good sense. This is because it largely follows speech patterns, as can be demonstrated by reading the examples above out loud. Incidentally, in both the examples with 'because' at Bristol, the main clause comes first, so I wouldn't have been tempted to use a comma in any case. But if the because clause had come first I would have used a comma, which reflects the pause we'd probably make in speaking. To reverse the clauses in the Bristol examples:

"Because the floodwaters were rising quickly, we all had to move to higher ground."

"Because she had already eaten a hearty lunch, she really didn't feel hungry."

As for the Oxford (or serial, or Harvard) comma, that probably depends on your educational tradition. I was taught not to use it (except where there is ambiguity), as I think were most Brits, but many American style guides advocate its use. It is, of course, the house style of the O.U.P. But just as I ignore them on the use of z in randomise/randomize, I pretty well ignore them on this one too.