I start playing it as soon as I see my first pip. I play in periodically here and there over the next few hours, then as soon as I see the beginning of a zip, I play it in a loop fashion until the job is done. It ususally does not take more than 15 minutes for my chicks to finish zipping once they start. Since I move my chicks out to the brooder during hatch I also use it for the following eggs. It's amazing how motivating it is to the chicks. (I hope no one removes that video from youtube, I'll be lost...lol) I actually think it's a better motivator than the actually chicks in the incubator...lolI never would have thought of playing the sound of baby chicks to encourage hatching. They perked up when I played it just now. I am currently at three chicks hatched, one looks like its about to zip. It keeps poking its nose out the hole and the others have gathered around. Ten eggs have pips on them so fingers crossed they all hatch.