I was talking to a guy at a spring shop in town about my rear springs on my 1989 Southwind 30E. I told him the springs were almost flat with little arch (with no air bag). He said many RV rear springs...
Re-arching is mostly a waste of time and money. The reason they went flat in the first place, is they were not up to the task to begin with. Quality replacement springs are the answer, or Timbrens. Air bags are adjustable, but have a finite life time under a MH.