Now that we have a house full of small electronic gadgets that require transformers to charge, etc. I'm wondering if there's any reason to unplug them from the AC outlet after your gadget has been fully charged? I was taught to unplug everything after I had finished charging, but my kids and wife just unplug their cellphones, iPods, etc. and leave the transformer/charger plugged into the AC outlet until the next charging session. Is there any reason NOT to leave it plugged in?