Since I'm generally only hatching abandoned eggs, left in nests partially or nearly totally at hatch point, I'm going to admit to never messing with humidity, gasp, opening the incubator during "lockdown" often, because they hatch days apart.And yes, I get some shrink wrapped chicks but I can tell by candling when it's likely to happen and watch to see if help is needed. I then dry them out, feed them for a few days then stuff them under the idiot broody who made all the mistakes and voila, happy mommy hen. Not all broodies know what to do, some get scared of nests, steal an egg from another hen that hatches early and leaves the nest too soon, cracks an egg, just up and leaves to steal someone else's eggs, or to start hatching the accumulated eggs of my non broody hens because she liked the larger number. And that's just a few examples. I have an incubator because a chicken has a brain the size of a marble and instincts aren't actually perfect. Peeping behind me are seven chicks who would have gone unhatched due to hen error. I'm going to stuff them all under the (more eggs are better ) hen tomorrow night. She'll be happy. Dry hatching keeps me from water logging chicks not ready to hatch, and let's the hatched chicks dry quickly.
I've been doing this awhile so I have challenged, used, and appreciated all the absolute rules of hatching. Use the rules until you get a real feel for the needs of your micro climate - no two houses are the same. Much less states or counties. I have multiple somewhat insane brooding hens at once, so rescue hatching is a lot more variable than a fixed point hatch. The rules are guidelines, guidelines that generally work well. But not for every situation or home environment. So take a deep breath and don't sweat a few variations from the perfect rules.
