Keets can stay in the hatcher up to 36 hours because they have just absorbed the last of the yolk right before hatching (which is why day-olds can be shipped w/o food and water), but it is recommended that you leave them all in until the hatch is over... In my experience with doing this the stronger more active keets will start pecking toes (and possibly navels too) and you will hear lots of screaming going on, and if your eggs are laying on the hatcher floor they tend to get kicked around a lot.
I usually wait until I have a bunch of dried fluffed keets bulldozing in the hatcher, then quickly open it and grab them all at once, trying not to let out too much moisture that can/will cause the egg membrane to shrink wrap down over the unhatched/hatching keets. (Sometimes there's a fine line between how long is long enough, and opening the hatcher and losing too much moisture and causing the unhatched keets harm). I also usually give the remaining eggs a quick fine mist with a mister bottle a clean water before I close the hatcher back up.
Sometimes the keets are dried and fluffed and doing well within a few hours after hatching, sometimes they need to stay in over night. I never take keets out before they are fluffed/dried and running around well. And if you see some crooked toes, it's usually best to leave them in a little longer.
