Yeah, it is something I have wondered about as well. The best I can do is leave a little out, or add a little bit depending on extreme temps. Thankfully, there isn't too much of a temperature swing here in Sacramento most of the time. I keep my truck tires at ~30psi. If I am hauling, depending on time, I either fill up the rears to 40, or all to 40. My trailer, I keep psi at max since at least half of the traveling it does is loaded and the tire wear from being maxed out and empty doesn't matter as much.