For many of us, our RV tires age out and dry rot before we wear them out.
I wish I could find a way to protect them so dry rot is not a concern. If anyone has any reliable data, it would help us all. I did some research years ago without any success.
Some RVers use tire covers. I doubt they do anything. The tire under the bed of my truck was obviously never exposed to sunlight but dry rotted anyway. Where I park, the drivers side tires are in the sun and the passenger side is always in shade. I see no difference in dry rotting based on the position of the tire and the exposure to sunlight.
I found no data to indicate any tire treatments help. Most are designed to achieve a dark shine and the treatment may actually be detrimental to the life of the tires.
I once tried 303 but without any success. There might be some benefit to the UV protection offered but again sunlight does not appear to be a major culprit. 303 also washing off and needs to be reapplied frequently.