leaving it charged is fine. I own probably 30-40 lipos between all my guns, rc planes, helcipters, cars and trucks. As long as you dont plan to leave them for like a year, you're fine.
trying to discharge it can be a termendously bad idea. If you let it get below 3.0v PER CELL - NOT TOTAL, it can literally explode in a ball of fire (worst case scenario.. best case scenario is you just destroy the battery but don't burn down your house or anything).
Now, please, google lipo safety and read up. I'll leave you with this:
LiPo fire - YouTube