When reloading and recharging mine and my wife's Sansa players, I had a tendency to plug them in and leave them overnight. Over time, my wife started complaining that she was getting only one day of play from the battery, when she had been getting two. My impression on lithium-based batteries was that they would not be damaged by getting left plugged in. sansa tech support told me that I needed to make sure I unplugged the player once it was charged. My battery seems to be functioning normally... Any input?