Here's what I do: Clean and wax the wheels, no tire dressing (on OEM tires like Dunlops it voids the warranty), inflated to max pressure (to allow for leakage and minimize distortion), individually wrapped in plastic bags, stacked horizontally on a pallet no more than two high, away from heat sources like a furnace, shielded from direct sunlight. This comes from my local race tire supplier, American's Tire Company. I've stored OEM wheels and tires for almost a year. Upon reinstall, the OEM's feel smooth, balanced, and show no signs of dry rot or ugly brownish residue from tire dressings.
'07 FJ Cruiser TRD SE 6M/T