as long as the veins are red, they will stay in the egg, because its the best thing to do for them.
as soon as the veins turn brown, they will hatch within 24-48 hours, because its the best thing to do.
patience. if the veins are still red, there still is more energy for them in the eggs, they need to suck that up first, when the egg is depleted veins turn brown and they emerge.