Perhaps the plastic bands can dry rot. But in a jam, that can be fixed.
Indeed, they do rot (the elastic bands). Spraying a mask and reusing it as was suggested by this moron does nothing, the masks are disposable because the media gets clogged with particulate matter and can’t be breathed through. At that point the mask is ineffective because with every exhale the mask’s seal to the face is broken.
I have some that have been in my garage since the obunghole 2009 epidemic and the elastic is still good.
Yep I have a small stash of about ten N95 masks. They are about 12 years old. They have been kept in the garage in a seldom opened locked cabinet. I inspected them last week and the elastic bands are iffy. I carefully stretched a few and the rubber discolored, a sure sign they don't have a lot of time left before they disintegrate.