How do you store your paint guns?

[fastfredracing]

I'm not a body man, so I generally only paint a few times a year, usually on my own projects .
So what I have always done was , after a good cleaning, , I would put maybe an inch or two of laquer thinner in the cup, seal it up good, and back on the shelf it goes till next time.
Seems to work pretty well. They are never clogged, and seem to always spray fairly well as soon as I pick them up. Am I hurting any seals or anything?
I left a few inches in my el cheapo harbor freight ( Primer, and tractor enamel usually through this one) and the plastic cup has warped a little since I last painted, maybe 3 months ago. Really well not a big deal, as these are expendable, but I've got a few that I like and want to keep them tip top .