[ A good question. It takes him a few seconds, but he's got it eventually: ] Just six months, I think.

[ Earth-months, obviously. Look how considerate he is, answering in a unit of time she'll recognize. ]

They say they'll send you home again if you're here for long enough. After enough building energy, or whatever it is we're doing here. No one's offered me any return trips though, so apparently six months' worth of energy isn't quite enough.