I leave my Lance 915 on about 80 % of the time, and have not noticed any loss of air in my air bags. I run them at 40 lbs loaded and 12 lbs empty. The only time I have had to add air is when I put the camper back on. I do check the pressure before heading every time.
1992 F250, 4x4, SuperCab, 7.3L Diesel w/Banks Turbo, 5 speed manual, Rickson 19.5 forged aluminum rims w/Goodyear G-124, 245/R7019.5 load range G tires, 5000lb. airlifts, Rancho 9000 shocks and Lance Lite 915 Camper.