You're not stupid. Your concern is absolutely correct... for everything else except distilled spirits (such as bourbon whiskey). Nothing in the world -- NOTHING -- can survive the ravages of time. All things deteriorate and eventually rot.
Except alcohol. Alcohol is antiseptic. It doesn't rot. It doesn't spoil. Of course, it doesn't improve, either (wine, maybe, but not distilled spirits). The result is that what you find in a properly sealed bottle of bourbon (or rum, vodka, tequila, or scotch) will be identical to what that bottle was filled with, no matter how long ago. One of our greatest pleasures is the feeling of being connected with history. No other product can do that. We have a bottle of Pennsylvania rye from 1916. My mother was born in 1916. When I drink from that bottle, I think to myself, "I'll bet my grandfather bought a round of this whiskey for his friends the night my mother was born. And it tasted exactly like this to them!".