They say they're working on it, but that they don't really know how it all works yet. Supposedly that's what some of the experiments are about; them trying to figure it out.

[Not that Derek buys that, but it's been repeated by enough sources, he knows that's the common consensus, at any rate.]

People do wind up going back home, just as sudden as they got here. Doesn't seem to be any pattern to it, though. They're just gone, and their stuff too. You'll hear people announce it over the journals when one of their friends has gone home.