What Alexiel03 said, until you know how long it takes your eggs to incubate and at what day your hatchling pip on average do not cut wait for the first one to slit.
If you can early you will expose your hatchlings to possible bacteria, eggs might dry out etc.
I let my hatchling pip, and if within 24 hours of the first pips the rest has not I simply cut the other eggs or if nothing has pip at 60 days I cut at 60 days because after years of incubating the same way I know that they all pip at day 59 or 60