How soon does an egg have to be put in the incubator?
Eggs do not lose viability unless they are held longer than 10 days after being laid. Remember that it takes a duck or goose about two weeks to lay a nest full of
eggs in the wild before they start sitting on them. So that first egg may be two weeks old before it is warmed up and development starts.
If you are holding the eggs yourself prior to incubation, a holding temperature of 55-60 degrees is best and turn them over every day.