Tire Dry Rot Is A Misnomer

First hand observation goes a long way. I am in construction and we have quite a few trailers of various sizes. From what I see, the spares seem to develop cracks long before the tires that roll do... For that reason, we typically replace spares when we replace tires, even if the spares have never been put on trailer axles.
No covers on any of the spares as in construction, they wouldn't last a week anyway...

I haven't read the article yet, perhaps later. Just stating my observations, YMMV