Too old to be crawling under the pickup to retrieve the donut spare
tire, and the "Xtra Tire" mount at $44 has proven to be useless, at
least for my '05 Colorado. So I smeared the donut with "One Grand
E.R.V. Dressing" tire protectant and now the tire is simply lying flat
in the pickup bed under chain and padlock.

Is the tire more susceptible to UV rays and dry rot lying flat in the
bed?

If so, should it be covered? I see spare tires mounted on the backs
of jeeps, etc. are covered with ? canvas ? vinyl ? and was wondering
if they are protective. Thanks.