When to use the Air system dump button?

I don't normally dump mine when just parking at the grocery store or short term parking like that. But eventually the air does all leak out. One thing I saw happen to a person who did not dump his air bags once was somebody took a chair out of the basement and leaned it on the rear tires of the motorhome. The top of the folded chair was under the fender skirt. As the air leaked from the bag the motorhome lowered and bent the chair and caused some minor scrapes on the fender skirt. Nothing major, but it would have ticked me off.