Obviously in nature, the eggs are laid together and it must work as there are wild chams.
Most people, including myself separate the eggs, allowing a little distance between each egg. It works well that way.
I have begun experimenting with keeping the clutch of eggs together and incubating them. The hatch rate is about the same. They all don't hatch at the same day, in fact it is similar to eggs that are separated. I have a current clutch of eggs that the eggs were kept together with no separation between the eggs. The clutch of 20 eggs began hatching on 7/28 and there are still two eggs to go. I would get 1 to 3 eggs hatch on any given day. About 1 1/2 weeks from the first egg hatching, I had 7 born on one day.
This isn't too out of the ordinary than when the eggs have a little separation between them.
All the babies are doing well, just as the case with the other clutches I have done this with.