How old is considered old? More than 10 years? Or shorter, like 5 years? I think most of the paper is stored in room temperature, not frozen.
It is also amazing the most of the papers do not have expiration date on.
For comparison, some of the Kodak BW papers have light sensitive materials in the paper. When the pager is old, it turns into grey by itself. Not sure if any color papers behave like that.