Any time that the internal temperature of the egg reaches 68° F development begins. Storing eggs at or above 68° drastically shortens the time that the egg will remain viable because you have a jerky stop and go mini incubation going on and this uses up the energy supplies of the egg and stresses the fetus before any real or meaningful development can begin. If this were not so then you could hatch an egg in your shirt pocket but the germ will die before it becomes a chick. Remember hatching a chick is a process that requires either you, or your hen, to follow a ridged sequence of events to achieve success. Hens follow this sequence of events because it is their nature. but we humans don't have the innate instinct to hatch an egg. This is why in a previous post I said that mechanical incubation is both work and problematic, while up to a point with natural incubation the less you mess with your setting hen the better her results will be, at least as long as you allow your hens to follow the basic parameters of chicken reproduction.
So it is advisable to remove every egg as it is laid and mark and date that egg then store it at 45° to 55° and 50-60% humidity until you can be sure your setting hen is committed to motherhood. Leaving eggs in the nest means that the eggs start and stop their development each and every time a new egg is added to the clutch.