Before I built the drive on ramps for my TA, I stored it for 3-4 months over the winter with no side effects. Every car is different but no problems on a GM f-body. I built the ramps for convenience of being able to jump in and drive when ever without having to move the arms. I have $200 in materials on mine.
The 2 x 6 supports under the LVL where ripped to fit in direct contact with the floor so the wood is all fully supported while driving on.
Sorry for the less than stellar pics, but its cold here and I didn't wanna pull the truck out.