As has been pointed out, Liquor doesn't age in the bottle. The cask itself and the surrounding atmosphere adds almost all the complexities (including the color - the alcohol itself is clear when it goes in) to the Whiskey. The alcohol actually saturates the wood, and gradually will absorb the local flavor. That is why Islay whiskeys have a "sea weed" or "sea air" flavor to them. The only other thing added is the distinctive "peat flavor" that comes from the smoking process that the grain undergoes in order to stop germination and prepare it for the mash in the tun.
Along those lines, Glenmorangie makes several lines of Single Malts that have been aged in barrels used in making other liquors - my favorite being the "port wine finish". As it ages, the whiskey takes on a distinctive "port" flavor which is actually quite good.
BTW - The one exception to the no aging in the bottle rule are undistilled alcoholic beverages such as wine. A good wine will continue to improve with age. Unfortunately though, 20 years in the bottle will not turn a bad wine into a good one. Some beers are better a few weeks after they are bottled (this is the case with some of the Belgian Ales), most however simply get stale with age.
- SEAGOON