I store them flat and level and with whatever fog juice is left in there. Hasn't been a problem. Always pick up the 400 watters half price after halloween. At that price they really do become dispensable. I don't trust any fogger and simply will not spend big dollars on one. 400 watt'rs as cheap as I can get 'em. Works for me with little to no pain, considering they're not breaking down and I have backups too!

Dan