I use a trickle charger to keep the planes I want to fly charged. If it has been sitting for a week or two, chances are it could have lost some of its charge and I won't fly it, it if has been sitting longer, I definately won't fly it. I used to never worry about it but I have some anal friends that proved to me that they loose some as they sit. I use an Ace Digipulse to keep 6 charged at once. Works pretty well.