Originally Posted by kwilkinson
They do change over time in the bottle. But most "dusties" don't change for the better.
Maybe if open and oxidizing, but generally, no, it doesn't. It's not wine, the much higher alcohol content keeps it stable. I've tried booze that belong to my grandparents, got packed away when my grandfather died and my grandmother moved to a retirement home, and was rediscovered a few decades later. Sometimes the maker changes the recipe or dilutes the spirit more than they used to, but the aging doesn't really affect things.
That said, some old bottles are indeed quite valuable- pre prohibition bourbon and rye, for example. Styles and yeast strains changed with the massive disruption in the industry, and collectors will pay a pretty penny for examples that made it through.
Oh, and as a further point to show that it doesn't change once in a bottle, some of the cognac makers keep libraries of their brandies, going back centuries, so they can ensure the product stays consistent. And the master blender gets to sniff (not taste) them on a somewhat regular basis, which would probably add a cool element to an already pretty cool job.