I agree, that is the key question. As I said before, this is like drilling for oil. It can be hard to say when you have hit "suitcase rock" and it is time to give up, pack up, and go home. For me it would be the time you point to. When Darden tells Rossi the control produced as much apparent heat as the test sample, and Rossi refuses to acknowledge that, I would say it's over.
The only thing I would consider after that would be for Rossi to hand over a single unit from the 1 MW reactor and have it tested by experts such as Murray, in NC. If he refused, I would have ended it. Perhaps I have a lower threshold than I.H. because I have seen many, many cold fusion claims fail.
yes, turn over a system to someone else, but I would only want 1kW not 1MW. I just don't like the idea of trying to do a good control run at 1MW.