Well I keep my 2010 MBP plugged in most of the time at my desk, but sometimes I will unplug it to use on the couch or at the dining table for maybe an hour or so. So I come back to my desk and plug it back in to the power when the battery is about 80%. Is it harmful to the battery if I keep plugging it in to charge after short uses? Should I wait until the battery is mostly drained before charging it again?