Originally Posted by
noglider
I recently read (here on bikeforums, so it must be true) that dry rotting comes from ultra violet and moisture. So be sure your storage place is dry.
UV, heat and ozone will indeed damage rubber. I don't think moisture is a problem with current synthetic (nylon, kevlar, polyester, etc.) casings as it was with the older cotton and silk casings.
To the OP, don't fold the tire for storage. Leave it flat and away from heat and light as above.