Anonymous wrote:The most damaging thing to tires is sunlight. Ozone is the second most damaging thing.
While you can’t really do anything about ozone, because it’s everywhere, the location of the spare keeps it from being hit with UV light from the sun. Because it’s protected, spares can last a long time. I’ve seen spares that were 20 years old and still useable.
It’ll probably outlast your car.
Depends. It sits pretty well out in the sun on my Jeep. But if you do a 5 tire rotation and replace the spare when you replace the rest it's no biggie.