I always bring my gear inside when I get home, not just because of heat, but also to prevent theft. It's not that I've ever had a problem with theft (with the exception of some kickin' speakers 20 years ago), but maybe that's why. When I was a kid we always had a convertible and it was pounded into my head not to leave anything in the car that I didn't want to have stolen.
Does heat in a parked, closed car damage things? I'm sure it does, but how much I can't say. I can say for certain that it does them no good.
A right emblem it may be, of the uncertain things of this world; that when men have sold them selves for them, they vanish into smoke. ~ William Bradford
I finally realized that Life is a metaphor for Fly Fishing.