You've nailed the typical reason for tire failure: under inflation.
Another aspect of tire performance and longevity is how fast are you driving?
Have you noticed if the tires blow on your way out, or on the return trip?
Do you also check tire pressure at the destination and has it changed (after returning to ambient air temperature)? Maybe there is a hole somewhere in the rim/valve stem/etc thatlets out sir and at some point, you reach the critical flexing of the side wall that causes a blow out.
Ultimately for me, it was speed that killed my tires. Once I slowed down to 60-ish MPH, I quit blowing tires.