Way back when there were large factory sponsored rallies we got to go to supplier seminars. I went to a couple held by Goodyear where some key points were made.
-Sunlight is not a significant problem. The real issue is ozone that is always present in some small amount.
-To combat ozone there are compounds added to the rubber. RV tires have more of it than truck tires.
-The anti-ozone compound only works when the tires get warm from use.
-If you travel a lot, your tires will be more healthy and be safe longer. If you are snowbird driving south once and north once per year, your tires won't be safe as long.
-Cleaning and UV compounds can aggravate aging.
We drove our Beaver a lot and put new tires on at 7 years. We sold it at 12 years. We we had no trouble. When Rick L bought it from where we traded it, he had a year or two left. I hope by now it has new tires!