It really depends what climatic conditions prevail at your storage site. The first winter with our Georgetown, I put the jacks down so as to relieve some of the load on the tires. Within two weeks, I notice a film of rust starting to show on the piston rods. I polished it off quickly.
I contacted the manufacturer for advice. They said "If you're close to salt water, don't leave them down without a protective wrap on them". I queried back on their definition of "close". I was gob-smacked when they said "less than 50 miles". We're probably 100 feet from a saltwater marina - the houses across the street have private docks!
What I've done since is to lower the jacks on one side to get both the wheels on that side off the ground, then I rotate the wheels 90 degrees then retract the jacks. Two weeks later, I do the same on the other side. Repeat the procedure four times on each side during the off-season. If we do take the rig out, I drop the next couple of procedures.
I don't know for sure if it helps the tires, but I don't get the flat-spot bumping of the tires for the first 5 miles or so first time out in the spring and the jacks are in fine shape.
Frank and Eileen
No longer RVers or FR owners