For those who have experienced this "degrading" of the plastic, can you post the conditions in which the masks have been kept? Do you leave them on the Bionicles posed, or stored among other lego? Are they exposed to direct sunlight often, or to smoke, or even aerosols? What kind of weather conditions do you live in; for example, hot and dry, humid, etc? As Toa_of_Regret mentioned earlier plastics eventually go through a break down process, albeit it usually takes a really really long time, however (and like a lot have mentioned already) there are things that can speed up the processes. As an avid toy collector I know other figures I keep are made of plastics that are more susceptible to things such as sunlight. So just curious as to what conditions the masks are kept in, for those of you who have experienced this.