I found a critical piece of info on the Bitconnect site:
"Though unlikely, Bitconnect reserves the right to disable the affiliate program and/or any given affiliate user any time"

Now I am beginning to think it might be sustainable because they can just disable the program for any user who is breaking the bank if things go bad.

And "Though unlikely, Bitconnect reserves the right to adjust the commission rate as necessary to ensure the continued operations of the Bitconnect service"

Now I do not know for sure they will honor their words but they have the options to make it sustainable if they choose.