I would say 24hrs at the VERY least. I would probably wait longer like 48hrs or not help at all if there was other chicks hatching as it will often dry them out as well. I only ever help if one seems to be struggling and all the rest have hatched.
It is definately a personal opinion and each of us make the decision on our own.
in my case the only reason I helped is that my humidity dropped in the middle of the night when I woke up it was 58 and 2 had holes in them. I upped the humidity and waited for a couple of hours you could tell they were breathing but couldnt move. I took one out wrapped it in a wet paper towel and carefully cracked some shell away. Then I could see that it was shrink wrapped. I wet the membrane put it back in the bator still no improvement so took it out again wet the membrane some more and started to remove the membrane after awhile got it out. She is fine. The 2nd one my hubby did. went to fast and she started to bleed, but she was out. I really thought she was not going to make it but within an hour she was up running around and now cant tell anything happened.. I have made sure the humidity has stayed up for the rest of the hatch. got 2 more to go.
Thank you both. I have one that pipped around 10am today, since, one more crack next to the original pip. It is going on 12 hours and I hear peeping in there but not sure if it is coming from the one mentioned or from the other 2 that have pipped so far. I just do not want to be this close and something happen that I could have prevented.