Just found this on another site! Does this make sense?
Normal Operation which Might Seem Faulty: The air suspension is controlled by an ECU under the drivers seat, which operates a solenoid valve block in the engine compartment. The ECU has a fairly low IQ, and wastes a lot of air by raising and lowering each corner constantly trying to level the vehicle. So the system's compressor turns on frequently. Another cause of its frequent running is the fact that the pressure switch is located remotely from the air tank so the pressure drop in the thin air line makes it think more air is needed. Another annoying feature that is said to be normal happens whenever the vehicle is parked on anything but a perfectly flat surface. The system tries to level itself by lowering all springs to the height of the lowest one, then realizes it is still not level so it lowers the first spring as well and starts the whole cycle over again until the vehicle ends up on the bump stops. This rather unintelligent strategy is particularly annoying off pavement, since the ground is nearly always uneven. So don't park where there is a big rock or other obstacle under the vehicle! If you want to stop in such a spot temporarily, either leave the engine running, or inhibit the system's unintelligent operation by leaving a door or the tailgate open. Pressing the manual inhibit switch on the dash also helps reduce or ewliminate this behaviour. Finally, whether on or off road, the ECU often lets so much air out of the system overnight that when you come out in the morning it can take several minutes for the suspension to raise itself up again to normal height. This is not supposed to happen but often does, even though the suspension checks out normally on the dealer's diagnostic apparatus