I would install tire covers to protect them from UV rays. I've heard that the plastic levelers now have a topper available to give the tires a flat surface to sit on rather than the pegs and holes. When I store mine I leave the Roto-Choks on with no problems.
Maxxair covers on your vents would help if you don't already have them. Saw a rig where UV rays deteriorated an unprotected lid and water got into the rig.
Dave & Jo Ann
'08 HitchHiker Champagne 35LKRSB | '11 F350 Lariat 6.7PSD