I had one last spring pip on the wrong end and it took over 24 hours to start zipping. I was a nervous wreck. I waited till the rest of the eggs hatched before breaking about a half inch of shell to help with zip, then about 15 mins later it was zipping the rest of the way fairly quickly. I'm not sure if I helped it start or if it would have preceded anyway. That one was the most exhausted when it finally hatched. It still slept for 2 more hours once I took the other out after they were dry so it was harder on it to get out.