I store mine with the upright arms spread apart, center arm between them (with the calipers almost closed). I put in in an out of the way corner, with a sewing machine cover on top to keep the dust off. I prefer to leave it mounted somewhere, but when I can't, I do the above. It's a sturdy piece, and you don't have to fear it losing adjustment because of 'bad' storage...the alignment should be checked periodically on a known good wheel, anyhow--no need for Park's 'centering gauge'.
It can even be done with a non-centered wheel, with a ruler and flipping.
*edit* I'm assuming you're talking about the TS-2.[x], but all the above holds true for almost any stand.