Robin,
Mostly it is a personal preference. However, this was a five egg clutch, and I am using some new incubation containers for the smaller clutches. Being a smaller clutch, I wanted to seperate it because of " head room" in the smaller boxes. My mistake came in seperating a clutch that could have been laid 24 hours before me finding it. Typically if you find a clutch within 2 to 3 hours of laying, the eggs come apart easily because they haven't "melded" yet (that's my word for it). I do not believe it is mandatory to seperate them at all, even if you are a "cutter", because they seperate very easily around day 50.
Hope that helps,