My experience with Apple has been similar, one time since I've owned them my iPhone has told me it was overheated and needed to cool down, and that was laying in the grass on a hot Texas summer day.
I use mine in a military environment so I'm not buying the kid gloves treatment thing, however I will accept that your environment might be rougher in that race truck. I just take a few basic precautions advisable for all non hardened devices, like keeping them out of direct sun, etc. My battery never drains when plugged in, but that's a function of the power provided by your USB device, and if you're using a 2 amp converter you're going to drain. Mine are hard wired.
BTW, I dig your IG and FB, i was about to order one of those flannel hats... but they arent on your store page yet :(
YMMV