AngBantamLuv
Bantam Chickens on a Pocket Prairie
Found an awesome explanation:I have a quick question, how long does it take after a rooster mates with a hen for her eggs to be fertilized, and how long can she lay fertilized eggs? Thanks!
https://www.cacklehatchery.com/how-long-after-mating-does-a-hen-lay-fertile-eggs/
Tldr; eggs will be fertile 2-3 days after mating, and continue for up to a month (depending on breed).