I left my pipe in my truck over the night. It was below freezing. I am assuming the pipe is fine, but I should let the pipe rest a while before using it. Is this correct?

My Sav has a balsa filter. I don't mind the filter as it doesn't seem to impede anything. How often should the filter get replaced? What is the difference between Balsa and paper filters? What is the main purpose for the Balsa filter?