Some of my paper is upwards of 20 years old.
Some of it is still as new. some is slightly fogged, but can be used with a little extra KBr of benzotriazol in the developer. Alternatively I can consider it pre-flashed and do no changes. Some of them are great for lith printing, even if they didn't work when new.
A very few (mostly KODAK) are completely dead, and seem to have no light-sensitivity whatsoever.