Rooster changes

[mustangsaguaro]

Right now all of my birds free range. And my rooster to hen ratio is to much so getting rid of 2 roosters. I am keeping 2 of my Lavenders. The girls I have are also Lavender and 2 Blacks (Lavender splits) So my question is this: I know at least one of the roosters that I am getting rid of he has been breeding 3 of my Lavender girls. Once these 2 males are  removed from the flock, how long will it take to safely say once the new rooster(s) start breeding these 3 girls plus the others can I start to use their eggs for incubation; and these new males,  the chicks hatched will be their offspring and not the previous males that were eliminated.

Thanks

[Schroeder]

Three weeks away from the old roosters should assure that all offspring are from the new males.