I cut all my eggs at Day 52, and I have no moral angst about doing so. I've seen at another breeder's location, two perfectly formed babies, that were unable to pip their eggs that drowned in their eggs - and you could see, when their eggs were opened, how they had thrashed about so much, they had ripped all the blood vessels off the top of the egg.
To me, that seems much more cruel, to allow a baby to panic to death and drown when it's unable to pip its egg. That seems terribly inhumane to me.
Some might say - they may not have been intended to make it then. And maybe they were intended to make it. Who's to say that something about the artificial incubation process didn't make that egg just a bit too tough for that baby to come out.
I made a choice that day that I will cut all my eggs on Day 52. Pipped or not. The ONLY time I've pulled a baby out of the egg was when I saw that their umbilicus was twisted around their body. I got them enough out of the egg to untwist, and put them right back in the egg, where they stayed until they absorbed the yolk.