I know we have discussed this quite a bit lately, and here is an interesting article regarding the shelf life of spirits compared to wines.
"Full-proof spirits don't expire," said John Bilello, brand manager for William Grant & Sons USA, an importer of high-end scotch, gin, vodka, tequila and other fine spirits. "After many, many years, you may have some evaporation, and the flavor profile may change, but only slightly. Most people probably wouldn't notice the difference."
By "many, many years," Bilello is talking 30 or more. By "full-proof spirits," he means distillates that are at least 80 proof, or 40 percent alcohol, the standard strength for most whiskey, vodka, gin, rum, tequila and brandy.