I researched this awhile back, and found that the manufactures recommend 10# over the cold inflation numbers. to help maintain shape and and eliminate flat spotting. Also they recommend to jack up each tire and rotate each tire 50% revolution wise to relieve the strain from siting for long periods of time in one spot.
Then before using your rig re-adjust the air pressure to what you want it to be. ( In the spring or after sitting for long periods of time, Change the air for fresh air and your good to go). and don't forget to do the 5th wheel (hitch) also.