The base liquors (brandy, gin, rum, tequila, vodka and whiskey) are typically the most stable distilled spirits and can be stored for a long time. Unopened, these bottles have an indefinite shelf life but once opened they may begin to lose certain flavor qualities over the years.
Liqueurs and Cordials:
The shelf lives of liqueurs are more temperamental than the base spirits because they contain sugar and other ingredients which can spoil, some more than others. Most opened (and well sealed) liqueurs should last for months and even years depending on their alcohol content and preservatives. Again, opened bottles are likely to lose some of their characteristics due to exposure to air. Once you begin to see any sugar crystallizing on the bottom, discoloration, curdling or other changes you will want to throw that bottle away or at least give it a taste test before mixing with it.
Cream liqueurs, those that contain dairy, cream or egg, are a different story and should be discarded after 18 months or so. Liqueurs like Bailey's Irish Cream, Advocaat and Amarula should be consumed within a year of opening, although some of their cheaper creamy cousins will deteriorate faster. Even in unopened bottles, these liqueurs will spoil and be undrinkable after a year and a half or more. Some of these touchier liqueurs will include an expiration date on the bottle as well. It is unnecessary to refrigerate cream liqueurs, but it can't hurt either.
Vermouths and other fortified wines have a much longer opened shelf life than regular wines. Typically, vermouth can be stored in an open bottle for at least a few months, although they can become musty and lose some flavor if stored for too long. Some people prefer to store vermouth in the refrigerator while others say that is unnecessary. I've done both and have not seen much of a difference.
Follow the recommended expiration date on the labels of all juices, bottled mixers (ie. Margarita or Bloody Mary mixes) and similar mixers. Usually it is best to refrigerate these after opening.
Club soda, ginger ale and tonic water should be consumed when they're opened or shortly after. If there's no fizz when you open a bottle of soda there's no point in adding it to a drink. If you find yourself wasting a lot of soda when making only a few drinks, buy the miniature bottles which typically come in packs.
Tips for increasing liquor shelf life:
- Keep opened bottles sealed tightly. Use the original cap, a replacement cork or the wine corks that also take the air out of the bottle.
- Never store liquor with speed pourers unless you're using them, these allow air to get inside the bottle.
- Avoid exposure to extreme heat or cold. Also, keep your liquor cabinet away from an exterior wall.
- Avoid bright, direct light.