Best surface for tires to sit on for extended periods?

Popsie wrote:
Don't let them sit on anything - jack them off the ground and use good tire covers.

Good tire covers I agree with. Jacking them off the ground, who does that anymore? Too much work and if I want to go I don't need the extra work. My rig sits on gravel with old rubber mud flaps between the tires and gravel. My last set of tires were 7 years old when replaced, without any problems.