Leaving them fully charged could also cause them to puff therefore damaging them. I've had it happen to a lipo before that I fully charged meant to take the RC out something came up figured next day I'd take it, rained, day after rain, day after rain forgot about it for 2 weeks pack was swelling. Leaving a LiPo charged for a day or 2 won't hurt it when its charged for multiple days it does damage.