How long is it safe to keep CDs in a 6-disc CD changer?

I just got a new car and it has a CD player that holds 6 discs. Is it ok to leave them in there for long periods of time? I have my favorites in there, so obviously I don't want anything to happen to them. Also, I live in Texas where it can get super duper hot in the Summertime. Is that going to be a problem?