It's my understanding If your on jacks " hydraulic" jack pads and they settle down, you have a hydraulic problem not a "air " problem. If you have air leveling.... overall air tank pressure is unrelated as a check valve prevents back flow into the tank and the bags should stay inflated .. If not they are leaking .. Many auto air level coaches have a electric compressor to keep the bags pressure constant and level (checking every 30 min or so)
If your just noticing when you raise your hydraulic jacks the coach is lower then the air bags have lost air with the system since they aren't leveling bags they have no check valve to prevent loss eithe the tank. And create another point to lose air also!
Air leak down in the tanks is almost impossible to stop just too many connections and like others I'm a comercial truck driver and have 0 air pressure after a day or more in my company tractor sitting this is normal ( a pain ) but normal.