I'd wait till day 22, then slip out the few that hatched and hold on tight for the rest! If temps were a bit low, they can go to as late as day 23, wtih a rare few lasting dill day 24. 25 is usually the end though.
I put mine in Brooder day after hatch. I just have my Brooder heating up as soon as first one hatchs..they have done fine first liter and doing fine now..