If there is no fall damage inflicted to a helmet, HOW OFTEN might one need to change out their old helmet? Do the materials in the helmet come apart from one another? I'm not really sure.. I have never crashed in the current helmet that I own, but it's like 5 years old and used daily... Any thoughts on when someone might need to invest in one? Also, I'm not sure if it would be helpful/hurtful to be in the HOT Arizona heat for a lot of the time.