When parked for a long time outside, it is a very good idea to get the tires elevated so that they do not sit in water. Blacktop and gravel driveways tend to "dimple" from the weight of the motor home and therefore create a puddling condition. Jacking up the tires is ideal, but even driving the rig up on 2" tall patio blocks is good, just so the puddle waterline is below the rubber tire.
The condition is more concerning in freezing climates. You really don't want the tires to go through cycles of freezing and thawing in puddles of water, especially on the same exact spot of each tire.
If your parking pad does not develop puddles where your RV tires sit, then you are in good shape. You don't have to fuss at all in that regard. It never hurts to put the max PSI in each tire as stated on the tires which for most "E" rated tires is 80 PSI. This way you minimize ground contact and have a better chance of having enough air in the tires in the spring time to drive the rig to an air station. Tires always loose air, especially from the swings in daily temperatures along with unseasonably warm days to unseasonably cold days throughout the storage period.
I agree that the sun can damage the tires so I think covering them is a good idea, as long as what you cover them with won't hold water and introduce the rubber-in-water condition.