I agree that under-inflation will cause a blowout. Unfortunately it is a science project to determine what the right pressure should be.
Our 2007 chassis has the original tires and I have no plan to change them anytime soon. I got 12 years from the last set with our first motor home. With our PC, the tires are designed to handle a lot more weight than actual weight so I think we are okay as long as the right PSI is in them.
Oh, our rig is stored indoors all the time as well, no sun, no cold, no dampness, etc. which helps a lot. 17,000 miles on them so far. They still look and smell like new.
If one of your duallies goes flat on you, better quick put 80psi in the other. It's always a good idea to carry a cheap 12V tire pump. I carry a repair kit like this one, bought cheap at Walmart. It looks big bit it is very compact. If the tire has gone flat because of a nail, I hope to fix the flat with a plug (not the Slime) while still on the rig. It's much easier than changing the tire. Then casually make our way to a tire repair shop for a better patch-from-behind repair.
