I know people have asked a lot about celluloid rot and how to stop plastic scales from degrading. Unfortunately even with a ton of searching I still haven't found an answer to stop the breakdown of old plastic scales (beyond the answer of; "there is no way to stop it").

However, I did find some helpful information to give a better idea of the cause along with some tips to prolong the life of plastics that have started to degrade...

Degradation of Polymers
Celluloid (Barry L. Ornitz)

hadn't seen any of these links on here yet but thought some of you would be interested.