Hopefully, ive heard it can sometimes last up to 4 weeks. But I hope I wont have to keep trying. I just want two hens from him. (Very high chances the one under the first hen is a boy) so fingers crossed!
Yes, I've also heard of eggs being fertile for up to 3 or 4 weeks after removing the rooster, but that seems to be fairly rare. So it really matters if you are introducing a new rooster and need to be sure he's the father of chicks, but I wouldn't want to count on it if I was trying to get a good hatch rate after all roosters are gone.