See for me, the cockerels and roosters are in a separate area than the hens.
Probly two days and you should have fertile eggs if they are laying regularly. This time of the year your probly doing really good if you get an egg every other day from a standard bred hen.(in natural lighting that is)
Jeff
On the clearing out of the others older semen to the newer cocks, there's lots of variables here I'd say from 2 weeks to 4 some rare instances proves the latter false also, not a set rule just an approximation is the best you could hope for here.
Jeff