I've always had luck at the 3 week marker.I used to have 4 black hens (now sold), to prove that viable sperm could last at least 4 weeks: https://www.backyardchickens.com/threads/why-are-we-black.1466402/
After 3 weeks, there was no longer a bullseye in the yolk, then I added the rooster. It's part of the technique I use.