A hen will have a better hatch if ALL the eggs are set under her at the exact same time---not some added a day or two later or 3 later. Example---If a egg is just added one day later---one day---its a staggered hatch set-up---with everything is going normal its going to hatch a day after the others. The others are dry---wanting to go get some food, If Momma gets off the nest---the chick that hatched a day later strength is not built up so it gets left---alot of times---and dies because it can not Keep up----Thats What I am Saying. A staggered Hatch Is Not Good and for sure does Not turn out good most of the time.
I personally with what most of you know---67 chicken pens, hundreds of hens have NEVER allowed a staggered hatch---All my broodies(72 in 2015 alone) have great hatches and I do not have to grab eggs and go put them under another broody hen or put them in a incubator or just let the unhatched die---I just do not let it happen, BUT that's everyone else's call if you want too!!