How long does hen stay fertile for?

[everyday_farmlife]

I'm really sorry if this has already been asked, but, I did a search and nothing came up...
So I got some really nice hens on the 2/09 so 12 days ago.
They are very close to SOP Light Sussex girls. They are getting on in age only reason we were able to get them!

Anyways they were in with a pekin roster so my question is;

How long will they be fertile from him?
They have been in with my LS Cockeral for almost a week, but, I hesitate to put their eggs in the incubator until I'm certain no Pekin x chicks are going to hatch I have nothing against cross breeds, we just have no use for them here (son is wanting to show the offspring)
TIA

 

[aart]

I hesitate to put their eggs in the incubator until I'm certain no Pekin x chicks are going to hatch

Then wait 4 weeks to be sure.

 

[everyday_farmlife]

Then wait 4 weeks to be sure.

Thankyou only 2 more weeks to wait then, we can do that

 

[sourland]

The general rule of fertility after removal from a rooster is: first week high fertility, second week moderate fertility, third week some fertility, and fourth week occasional fertility. That being said, there are always exceptions. I'd start collecting eggs after two weeks away from the cochin.