all seeds are different. there is no exact answer. I've left seeds up to a month to see if they pop...never have, but I still left them that long. Usually with-in a few days to a week on average.
I smash my shit with a hammer, and say west side. if they crack they aint no good. But honestly just wait awhile float or not floating doesnt make a difference if its dead or alive. It will crack eventually.