Good topic.
I dont store them, but if I do, as in 'not get out', Ill leave them as is really. There only ever around the middle, as you point out, 150'ish, anyways. But I have stored my HM with a full tank before. For a while too. No problems with performance either. I think I like to think I like to keep the pressure as high as possible... I dont know why and I dont fully understand if this is a good thing. Theory being, if somethings full, nothing can get in, so to speak.
Thinking though, say you were gonna store a rifle which had a full tank, would you just run it down before hand?