We had really good results from eggs up to 3 weeks old with the regimen I mentioned. 70+% hatch rate. Of course, that 30% could have been the oldest - I'm just going on the info I've found.
A fertilized egg will only develop if it has the right conditions - temperature mostly, so collect them...
Welcome to the grand experiment! You are in for a treat.
Ok, a few things
Fertilized eggs can be kept for up to 3 weeks for hatching. They should be kept warm (15°c) and should large end up. Turn them once a day, along the equator - mark one side with an X and another with an O so you can...