I've heard they can go without food and water for 2 days, though I haven't left them that long. I have had a couple of chicks struggle to get out because they pipped low or missed a spot when zipping, so I've let them struggle for 24-36 hours before helping them. I do try to help them as little as possible so that they still have to fight to get out as they need the exertion to strengthen. Generally it's best to only open the incubator every 8-12 hours, though some will let the whole batch hatch before taking them out.
I'm not certain what advice you're looking for, but I'd leave them for 24 hours and, if there's a reason they can't get out, beyond weakness, that's when I'd help out. When I do help, it's to break a piece of membrane that's stopping them or gently open the shell a bit. It's important to make them hatch.