I like to listen to my iPhone 4S's music at work via iTunes/USB cable through my PC speakers. Will this hurt my battery doing this every day? My only fear is over-charging. But I hear that the iPhone automatically stops charging at 100% (or rather, only trickle-charges at a very low rate). Is that true? Is it safe to hook my phone up to my PC through iTunes every day to listen to music? Or am I killing the battery faster doing this? (Same with any iPhone dock - is it safe to use it in the car via a FM transmitter/charging station every day? Or should I stick to the Cassette Adapter through the Headphone jack?) Normally, I charge my phone to 100% and then leave it unplugged until it get's under 20%. But I'd like to listen to my music more often at work through the USB cable and iTunes, regardless of the current phone charge. Anyway, is it safe to keep it plugged in all the time?