I won't quote it all, but mil-spec requires vertical storage (when possible) in dry place, 32 - 85 degrees, away from contaminents such as oil, gas, jet fuel, etc. and away from electrical motors, welders, fluorescent lights, etc. (ozone producers). The vertical positioning is mostly to tell folks not to stack them flat and on top of each other causing distortion. We are required to store aircraft tires standing up in specially made racks.
If it will be a while, I would find some way to wrap them up or cover them somehow. Maybe a large trash bag, plastic moving wrap, etc.
Seems like a fair price though.