Sun IS very hard on tires, especially those that are always in the same position (spares - and especially spares which get the same sun angle everyday or are always parked outside). The excessive heat dries out the compounds and makes them crack easier/sooner. Ever wonder why RVs are stored with covers over the tires . . . or why the tires on my cargo trailer are shot after seven years of sitting outside ?
The five tire rotation will help them all age at the same speed and frankly, to those that don't do a five tire rotation, I cannot fathom why you would not want to get an extra 25% + mileage out of your expensive set of tires.
I know most on this forum think showing off their "big ol' tire" on the back is really cool or they have a backup camera mounted there but I took the practical step and spent all of $20 + shipping on a vinyl tire cover from
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