Far as I know it makes no difference.. However I would put blocks under the jacks,, I might put lumber under the tires as well (At least a 1 by 12) just to lift them a bit off the ground.
You might also wish to cut plywood "Toumbstones" and put them against the tires then put wheel covers over the lot to protect from sun as well.
(Plus they make good screens for my holiday scene projector)
Home is where I park it!