I don't know if anyone has ever collected any data to see if there is a "sweet spot" for moisture content of a sensitized tissue.
This is what I was referring to by "conditioning"; some specified moisture content may not be particularly sweet, but if it affects the chemistry, it would be nice to have it the same every time. "Fully" dehydrating (silica gel, molecular sieve, etc.) for storage and then conditioning to a predetermined moisture content (calcium nitrate slush, etc.) might be a worthwhile technic. I haven't worked with carbon tissue, but I understand that it is plasticized with sucrose, which would seem to be most effective if not completely dry.
Regarding refrigerators, I was thinking of the dorm-room size, or maybe one of the under-the-bar refrigerators.