Haven't had a flat spot on an RV tire since I replaced the nylon tubed tires on my 1972 Lifetime MH. Those tires rode really rough for a couple of miles, especially in cold weather.
Leveling jacks are to level the MH, for as long as needed. For 12 years my HWH jacks stayed extended for at least 6 months each winter in FL and never did anything special, nor had a problem.
I had 19.5 Goodyear 159's and the later 670's blow at 5 years. Not overloaded nor under inflated. No damage from the 159 blowout. The 670 blowout did over $2500 damage. None of the tires had any visual queues (weather checking etc) of impending failure.
From my 50+ years experience driving RV's I'm a 5 years and out guy. I don't cover my tires for for the 6 months they endure the FL sun, and have never had checking from sun exposure. YMMV.
No comments here on stored tire contact with ground, blacktop, or concrete and damage from leaching of the chemicals in the tires. Tire specialists have told me it is a problem. I have no proof, but always store mine with wood or plastic carpet runner under them.
