Once she starts sitting the eggs start to develop right away. So after the first day you need to remove any new eggs or you will have a staggered hatch. The danger in that being the broody mama might abandon the eggs that are late hatching to get up and take care of the newly hatched chicks.How many days should go between first sitting and not letting the other hens donate more eggs?
I had a tiny frizzle bantam Cochin that I got lucky with and she sat for 3 days after the first one hatched and all were fine, but that isnt always the case.
Does that answer your question?

Marie