I stored two sets of Goodyear originals, one set for 20 plus years, stacked flat (first tire on wood), separated by a single layer of plastic to keep the carbon black from penetrating the white letters. Light coat of protectant on the tires, otherwise they sat in one spot for all that time in a frame garage, not climate controlled, and were dry-rot and check free when I sold them a couple of years back. If you store them for a long length of time upright, they'll probably flat spot (my B.F. Goodrich T/A's were terrible after 19 years in the same spot, no dry rot amazingly, but were quite square). The Goodboots were not mounted; the T/A's were on my LS5 Chevelle, sold in 2011.
BTW - the T/A's did not rot, either, but I sure wouldn't have run them on the street - felt like a Shriner's clown car when I pulled it out of storage.