One of the reasons that I check the eggs daily is so that I can determine when I see the first pip mark. I make a note of the time, and I know from my experience that I should have a live chick within 40 hours. Anything past 40 hours and there is a very real possibility that the chick will never get out of the egg without assistance. Average hatch time for Peachface, Fischer's and Mask Lovebirds is 40 hours. It takes that long for the chick to pip around the top of the egg.
Pip marks follow a pattern.
If the marks look erratic or irregular, the chick may be in trouble. If there doesn't seem to be any progress, the chick may be in trouble. From my experience, it takes 36 - 40 hours for the yolk sack to absorb. Once the energy source is gone, and the chick is still not out of the egg, it will become frantic and begin to chirp. If you don't open the egg, the chick will die.