I was about to say. They stop crowing about the time you start cutting up onions for Chicken and dumplings.Approximately the day after they start if you've got a knife.
To the OP: sometimes you just get a slacker. I don't particularly pay attention to when mine start, because I have about 10 at any given time, but I do remember one that took 24 weeks off the top of my head. I think I've had longer though.