I think the biggest threat would be UV light, which shouldnt be a problem since everyones CDs are in cases (I hope
).
Ive got an interesting story about plastic, actually. I have a General Electric alarm that ive had since elementry school, which makes it at or around 20 years old. Ive been using this thing as my main alarm clock all this time, and it just now in the last year started giving my problems. The slider switch was acting up. Rather than getting a new one, i decided to fix this sucker since its been with me so long. Upon trying to take it apart, all the screw posts pretty much shattered like glass. Its just the plastic finally becomming brittle because of age. Well, i was able to fix it (turns out it had a little bit of corrosion on the board. I must have got the thing wet at one point over the last 20 years
). I just had to use a little glue to put the case back together, but it looks great and still works.