Pullets are being bred, how long until eggs?

[Queen of the chickens]

My Cochin Bantams are around 17-18 weeks old. The Cockerel's have started mounting the pullets (much to their dismay). There is a Belgian d'Uccle that they have been breeding for almost 2 weeks. How long do you think it will be before she lays? (Her comb and wattles are red.)

 

[TaylorHobbyFarms]

If her combs and wattles are red and they have been mounting her, I would assume it could be anyday. All breeds and the individual chickens themselves are different as to when they will start laying.