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Originally Posted by railwayman3  Refrigerating and especially freezing will increase the life considerably, up to several years, but common sense is needed and older film would need a test before use...... |
I'll add this: AFAIK, there are basically two causes of deterioration of unexposed film over time: chemical changes in the emulsion and exposure-like events caused by radiation (including cosmic rays). The chemical changes can be slowed substantially by cold storage, but radiation -- and particularly cosmic rays -- will continue to affect film no matter what. There really isn't much you can do to protect film from cosmic rays, since not even lead stops them.
This is relevant because the speed of film affects how quickly it deteriorates from cosmic rays. Thus, all other things being equal, you'll get a longer useful cold-storage life from a slow film (say, Velvia 50) than from a faster one (say, Elite Chrome 400).