Its a good question. In my experience you have a few weeks. I have always left them 2 or 3 weeks from first spotting them coming in season with no problem. However, I once left a jill in season for too long, probably between 4 to 6 weeks and even with a jill jab that took her out of season, the hormones had started serious biochemical changes and she developed anemia that was irreversible. Horrible mistake to make