[Motor31]

Your best option is fairly simple. Do not let them sit on the same spot all the time. Take the RV out and move it a few miles once a month to get the tires some "exercise". That will stop the deterioration from sitting in one spot and causing stress to set in one place on each tire. It also moves the internal oils in the rubber so one spot does not dry out. A secondary effect is to make the grease in the bearings move and maintain flexibility as well as helping prevent brinelling of the races when the rollers stay in one spot all the time. When you come back to the space, put the tires on wood or plastic sheeting. Do not use tire dressing on them as that tends to accelerate the deterioration of the rubber because the dressing contains petroleum distillates.