I need a rechargeable trackpad for my Mac Mini setup, and I'm considering something like the Logitech Trackpad. I've found some refurbished/used options in addition to buying new, and I was just wondering: -Will a used trackpad have a shorter charge life than a new one? -If the unit loses its ability to hold a charge, can I still keep it powered merely by leaving it plugged into the USB connection? I have no general issues with buying pre-owned stuff, but it never hurts to know these things in advance.... Thanks!