Preserving tires

Factual Questions
1

We bought a '94 Suburban 1500 back in September for a song because of the gas prices. It sat for about nine months and is wont to happen here, the tires that came with it have sun-rot – sidewall cracks and just general unpliableness of the rubber. So, it’s time to get a new set of tires.

It’s not being driven much. My roommate has a five-mile round trip to work plus a few dozen mile per week for errands. It’s taken on longer trips to dogshows and the like a couple times a year, and that’s it; I’d guess 5,000 miles a year tops. Unless something is done, sun-rot is going to get the new tires long before the tread is gone. Will Armor-all or something similar help with this? Is there some other product that will help keep the new tires “springy fresh” in this hot climate?

2

Most tire companies advise not to use any tire dressing.
However Michelin has recently introduced one that they do recommend (imagine that).

We motor home owners often use tire covers made for the purpose of keeping the sun from reaching the tires and also put something between the tires and the surface they are parked on.
That is what Michelin recommends in their RV tire guide which can be found on their web site.
I would expect the advice would also apply to passenger car tires.