Cut no earlier than day 52.

Another reason to wait, based on my experience is that as soon as you cut, your brain will tell you that they should hatch the next day. I have cut as earle as day 47, and the wait for them to come out once I knew what was in there, was DREADFUL. This year, I plan on cutting no earlier than day 53 (most of our eggs were cut on day 49 last year).

Hope that helps,