Yeah, that thermocycling is hard on them... metallurgically speaking.I think you should store them in your freezer so they stay used to cold temperatures. (I don't do this though, I just hang them on a hook)
What a neat tractor! If they had tractor demolition derby's, I'd bet yours would come out unscathed.
I just cant understand how people work in the woods with their farm tractor and not get a branch side the head without a screen for protection.