I wouldn't really say that there is a concensus, but data from several studies points to 6-12 mmol being the optimal dose, at least in healthy young individuals (we are presently conducting dose-response studies in heart failure patients and in healthy elderly individuals, as they may require more).

As for chronic vs. acute dosing, there really isn't much evidence in humans for anything beyond an acute effect (as I had to educate a reviewer about recently).