Another camper asked me if he could shoot my white tire covers with his IF gun. We both were sitting to get full afternoon sun. He found his black tire covers would go to 160 -165 degrees on the inside vs 105 inside my white tire covers. Outside temps were in the low 90s with full sun. The trailer was set up for a 45 day stay at a KOA. Other wise I don't carry the covers while on a trip/vacation.
Of course we know that sun rays kills tires rubber on a sitting trailer (months at a time)......Heat also is a rubber killer.
There are no trailer tires (ST) that recommend 7-10 years before replacing. Most say in the 3-5 years range.