I have set my tire pressures at 110 psi cold for the front 6 tires, and at 100 psi cold for the 2 rear tires. After less than an hour at 50 to 55 mph the tires rise at least 15 psi. When I first purchased the coach two years ago I was advised to keep the tires at 120 psi cold. The potential problem I saw was that in warmer weather, after an hour at highway speeds, I would see the tires go as high as 140 psi. I then saw somewhere (was it here in the forum?) that the wheels also have a psi limit. Thus, I moderated the cold pressures such that the tires would not exceed 130 psi when at highway speeds.
The front end of my coach weighs just over 16k when full of fuel. The 295/80 22.5 Michelins on my coach are rated at just under 8k at 120 psi. Thus, I figure at near 130 psi the coach's front end weight and the tires should be in sync. But, there is always that first hour to think about, and there is always those colder nights to think about when the cold pressures will not be up to 110 psi cold. For those circumstances I try to seasonally adjust the pressures to account for cooler and warmer nights. I have not often, but I have occasionally, stopped along the road in a wide spot to add air to the tires if I see they are too low.