That is a possibility, but then, what determines when payment time comes? I can't say for everyone else, but my invitation didn't have a clause about staying for a limited time. And given that those that have disappeared seem to have been here for varying length of times. Some recent arrivals, other's having been here for years. It's too common to be sporadic, and no apparent pattern as to what or why it happens. Those in power either do not know why it is or have not been forthcoming in answers. Either way does not seem to bode too well.