Charles Thomason, a veteran distiller who started in the business before World War I, wrote notes in the 1960's on how to make good whiskey. They were printed in the 2002 Bourbon Festival Magazine, entitled, "Making whiskey in the bluegrass". Here is a quote:
"...many distilleries are going to be disappointed in the old whiskey they are going to have on hand in the next twenty years. The old bonded period was eight years. Today the bonded period is twenty years. But as I have told you of the seasons cycle, and the tannic acid is out of the wood and it begins to deteriorate, and since whiskey takes up other tastes and odors, it easily begins to take on a 'punky' or rotten wood flavor, and the longer it stays in the barrel, the more it takes up... Now this old whiskey goes down very smoothly, but leaves a 'punky' aftertaste. So if you want to taste the best whiskey with the best taste for the best price, get four-to-seven year old whiskey, for a seven year old whiskey has reached its peak of bouquet".
Thomason adds later in the article that in some modern warehouses, the air does not circulate well and also is warm too much of the time. This, he says, allows too much tannin to get into the whiskey because warmth leaches tannin from the wood but there aren't enough cold cycles to draw some of it back into the wood, as was done traditionally under Mother Nature or by careful regulation of the heat artificially. He says large modern distilleries are risking making bitter whiskey because they don't let it cycle in the traditional way.
In sum, he was saying long aging is not a good idea because ultimately too much tannin and off-taste gets into the whiskey (no matter how it is warehoused); and also, there is a risk of tannic whiskey even with moderate aging because the modern warehouses of big producers (he seems to assume) are not properly ventilated and/or too warm.
My impression of modern long-aged whiskeys, and younger whiskeys made by the big houses, is that they do not reveal the tastes he is talking about.
I enjoy well-aged whiskey and while clearly it shows more of the barrel than younger whiskey, I don't detect the adverse effects Thomason predicted. Nor do I see them in younger whiskeys aged on pallets in modern warehouses. Just tonight I had a Jack Daniels, which I assume is aged in modern warehouses. It tasted of fresh wood and corn and butter with light char flavour and the perfumed taste it is known for, nothing punky about it. I have had some old scotches that have the taste he is referring to, it is the taste of old wet wood, old wet oak, slightly musty. Rarely if ever have I noticed this in bourbon old or younger, however.
Was he too pessimisitic about the ability of modern methods to produce (old or young) clean-tasting whiskey?