I've got an expansion tank in my attic near the hot water heater and the air psi in the expansion tank can vary 5 or 6 psi depending on the air temperature in the attic. I live in Texas where it gets very hot, and freezes from time to time. I added air when the temperature was about 70* or so thinking that is a good median temp. Any other tips or ideas? Is that much of a difference a big deal? Should I wrap insulation around the tank? Thanks in advance.