The tea-bag effect of aged spirits AARON COHEN · MAR 21 2013
Because of the tea-bag effect, after a point, spirits don't necessarily get better the longer they age. Bottled liquors don't age positively at all which doesn't have anything to do with tea bags.
What distinguishes these two approaches is what Pickerell refers to as "the tea-bag effect": The first time a tea bag (or barrel) is used, there's more flavor to draw out. Resting in brand-new barrels, bourbon needs less time to extract what Pickerell calls "wood goodies" -- it sucks vanilla and caramel flavors, as well as spice-like notes, out of the wood with ease. Many of those same bourbon barrels, once emptied, make their way to Scotland, where they are used to age Scotch whisky. At this point, most of the "wood goodies" have been depleted, so scotch often needs a longer aging time to suck out the remainders. Evaporation plays a role, too: In the dry climate favored by bourbon distillers, liquid evaporates more quickly, and the product becomes concentrated more quickly.
Also, according to the article, the ideal age range for whisk(e)y is as follows:
Rye whiskey: 9-11 years.
Bourbon: 6-10 years.
Scotch: 20 years.