Our previous coach came with a sleep number mattress.....what a piece of JUNK! The first year the motor was replaced under warranty as were the wands. Soon after, the new wands wouldn't show the number but worked. That lasted about a year then the mattress would loose air on one side.
We threw that mattress away in a dumpster in St. Charles, MO, and had a regular Beauty-Rest mattress delivered and installed at the motorhome.... the best thing we ever did! I will never own another sleep number mattress again. (And, ours swelled too going through Colorado).
The new 'regular' mattress was thicker (and so comfortable) but it was difficult to raise the lid under the bed. I only kept extra sheets and the bedspread (decorative) under there. I could hold the lid up with my shoulder if I needed to retrieve anything.
When we sold the coach, I bought a new RV mattress at Camping World and took the Beauty-Rest to use on a guest bed at the house.
When replacing a Sleep Number, you have to make sure that the new mattress fits when the slides are closed and make sure that the new thickness doesn't block any light switches next to the bed.
Safe travels,
MM.