Thanks Gerald for the explanation of the sidewall flex being the main culprit of low inflation; I knew that but couldn't have explained it as well. At rest stops and camp setups, I infrared gun the coach and toad tires. Of note is the fact that inevitably the tires on the sunny side will be hotter than those on the shady side, whether I check them cold with a guage and infrared or hot with just the gun. Even the wind on one side can make a difference, or if one tire is on asphalt and others on gravel or concrete. So be careful when noting differences between tires of 3-10 psi. I try to adjust air only when all are equally shaded and exposed and fully cooled down; early morning commonly fits the bill.
Not sure why Mike couldn't get his coach inflation apparatus to work; the one I made as per the popular YouTube video works just fine, and is faster than other modes I've tried; admittedly I haven't headed north of about 115 psi, but it sure seemed to want to if I let it. It could be his tanks are set to top out at 120, whereas mine seems to be closer to 130. Otherwise I also would've purchased a ViAir compressor. But as Gerald also notes, it seems Mike needs a new auxilliary unit up front under the passenger side, although he doesn't seem to believe he has one.
I'm not familiar with coaches with the additional hydraulic leveling, but if his air leveling-only operation isn't compromised in any way by the hydraulic side, auto air level should mean an auxilliary compressor that maintains level as Steve mentioned. Plus when air dumping or something during leveling diminishes my tanks much, I just restart the engine briefly to punch them back up; as long as I don't hit the Travel Mode button, or have a slow leak, they maintain full and the coach stays where I leveled it.
Joel