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Stored at room temperature, Alkaline batteries will retain at 80 percent of their original charge for around 7 years. In another 7 years, they'll have 60 percent of their original charge remaining, and so on.
Storing them in the fridge greatly increases their shelf life, and storing them in a hot vehicle greatly decreases it:
So, unless you're planning on using them all up within a few years of when you bought them, it's best to store them in the fridge.
Lithium cells still have around 80 percent of their original charge after being stored at room temperature for 20 years, and will probably outlast any fridge you store them in:
http://img545.imageshack.us/img545/604/lithiumshelf.gifIt only takes a couple years for Carbon-Zinc batteries to drop to 80 percent of their original charge. However, keeping them in the fridge has the same beneficial effect as with Alkaline or Lithium batteries - they'll store a LOT longer that way.
When storing batteries, it's best to seal each battery individually in plastic (i.e., Saran Wrap, zip-lock bag or vacuum-sealed), rather than storing a bunch of them together in the same container. This precaution ensures that if one battery leaks, it won't be able to leak on any of the others. Sealing them in plastic also helps keep moisture out, which prevents condensation from forming on them while they're in the fridge.