I went out of country for what I was told was going to be 3wks and wound up being gone almost 3 months. I had stored 7 lipos at 50% charge and every one of them had puffed a cell - the cell on top the way they were sitting.

If I don't use mine every month, I discharge it at 1C, then charge it. I prefer to use them when I can however, which has been a real prob thanks to work lately.