So, Apple recommends that the MBA's batteries get "exercised" a bit... meaning to unplug every now and then to let the batteries drain. If you're a user who pairs the MBA with the Thunderbolt Display at home, and rarely take it off the plug to take it on the go, what do you do? Do you just sometimes unplug and let the batts drain a bit? Or do you just leave it plugged for days, weeks, months? on end? Also, follow up question: if say one day in the future, the batteries do die, can you just leave the Air plugged to the TBD and it'll still work, and just be powered by the TBD? Thanks.