[quote="David A. Goldfarb"]The slower the film, the better it keeps. I try not to keep 400 or faster films around too long, but I've used slower films that have been more than 5 years past expiration without serious problems.
High speed films will fog from cosmic rays and you really can not protect from this. I exposed two boxes of 12X20 Super-XX film last year that had been stored in a freezer since it was purchased fresh (from a special Kodak run) in 1989. The film had a b+f of about log 0.50, in contrast to about 0.15 which one would have encountered when this film was fresh
Low and medium speed films do much better. I recently exposed a roll of 220 Plus-X with an expiration date of 1992. Its b+f was only about 0.15.