Most foods progress from wholesome to hazardous in a relatively short time, depending on their ingredients and how they’re stored. That’s not the case with your liquor cabinet, where distilled liquors remain drinkable — from the food safety perspective — almost indefinitely. Quality is a more subjective measure, and you might occasionally find it necessary to replace some of your older bottles in the interest of better flavor.
The Hard Stuff
Hard liquor is a long-keeping substance, precisely because of its high alcohol content. At 80 to 100 proof, or 40 to 50 percent alcohol, it’s a potent antiseptic that kills bacteria and molds on contact. It won’t improve through bottle-aging, as wines do, but won’t become unsafe either. The issue is that the liquor’s delicate flavor compounds, which make it distinctive, are vulnerable to the effects of light and oxygen. Once you’ve opened the bottle, it can lose its subtle nuances in as little as six to eight months. This isn’t a concern with inexpensive brands, which have little subtlety to begin with, but nobler spirits should be consumed within a few months.
Liqueurs are more variable, in part because their alcohol content can be as low as 15 percent and in part because they often have added ingredients which affect their durability. Simple herbal liqueurs typically last as well as hard liquor, though with the same limitations on their flavor. Sugary sweet liqueurs can attract insects, and over time their sugars can crystallize unattractively. They’re still drinkable, as long as neither of those two problems occurs. Cream liqueurs are the most perishable, because of their dairy ingredients. Some specify refrigeration after opening, and can curdle and spoil like any other dairy product if left out at room temperature. Drink them cold when applicable, or warm them gently in your microwave before adding them to hot drinks.
References and ResourcesSerious Eats: How Long Do Spirits Last?
The Kitchn: Does Liquor Ever Expire?