1) I would top off the mags after you shoot a mag, cool down will affect your next mag (temperature, how fast you shoot, etc.)
2) If you're storing them, I would release all the propane, but don't hold down the release valve and let it all out at once, let it out in puffs...(lightly push it for 1s each time, until empty)
Then you would add some silicon oil in the fill valve and add 1-2s of propane for storage (green gas works too)
If you leave the mag empty chances of a leak occurring is high. Make sure the o-rings are well oiled as well.
3) Make sure you clean your inner barrel as well as clean out the gunk from your gun and lube it again - silicoin oil (or RC shock oil) for plastic and O-rings (15-30WT), and grease(Canadian tire
http://www.canadiantire.ca/en/pdp/pe...0813p.html#srp) for metal on metal contact (e.g slide)