If they are well capped....pretty much forever.
Linda C

There is a shelf life on alcohol, but it varies with type alcohol and amount in the bottle.

Alcohol evaporates over time, (in the liquor business this is called the Angel's Share, cute huh?). So an unopened bottle has a higher proof than an opened one; and a half full bottle is higher in proof than an almost empty one.If you've got bottles with very little in them and have stored them for many years they're a toss.

Open bottles of cream based liquors, ie.Baliey's Irish Cream, can coddle with heat, high proof alcohols and acids. So check before you drink and if it hasn't been used in about 2 years toss.

Any bottle that has real fruit in it, ie. the pear in the brandy bottle etc. ,should be checked if the fruit isn't completly submerged in the alcohol toss it it's rotten.

Sugary liquors can crystalize out the sugars, so wipe off the lips of the bottles after pouring, and nasties won't grow there in you cabinet.

Other than that why keep stuff that you don't drink, toss them of give them away, and use the space for something else.

Hope this helps.

After both my inlaws passed away, we cleaned out their house. Found lots of bottle of liquor. We have opened and tasted the contents. Even after more than 50 years, everything has been good. One had a label we know came from the 1950's, because it had a phone number in an old 6-character format that was replaced in 1955.