I have 4 planes that use lipo's all are Parkzone or another brand. Whether I use them a lot or little they all are puffed up. I had one puff up after only one flight. Maybe I shouldn't use them, maybe they are OK, I really don't know. They charge fine, the flight time is as expected, so I continue to use them. I do charge them in a charging bag just in case. I figure if they fail in the plane or catch fire, it won't be the first plane I have lost and probably not the last.