In time everything loses its shape a little and may accommodate a ding or two by normal wear and tear. So that depends on how much you handle it and how hard you are on handling your device in its case.
Nope. High heat on the other hand is not so good. Personally though I can't think of any reason to leave your phone in a closed window car parked in the sun over multipe hot summer days. Even then it would take years of such abuse.