Once I place my eggs in my hatcher. I never open the door. I have a clear door which helps so much. You want your humidity around 70%. Everytime you open the hatcher, incubator, you are letting out heat and humidity. That is hard on the chicks pipping, and just hatched. Let everybody hatch, and then open the door and take your babies out. You treat your newly hatched babies, well like babies, let them dry and rest from hatching. It hard work for them.
You Have To Figure Out What Works Best For You Because Not Everyone Does The Same Thing Like I Said We Run 35-40 And 65-70 At Lockdown With A 90%+ Hatch Rate
I think it depends on what incubator you have, the humidity surrounding it and the time of year as well. It also depends on the size of the eggs also, from quail to goose. Here I dry incubate my bantam eggs (30-35%) - then at day 19 take them out and put them into my hatcher to 40-45% humidity and leave them to rest, I just then wait for them all to hatch in there. Do not forget, the more that hatch, the higher the humidity becomes so some late hatchers can drown! Water makes chicks bigger in the shell so that sometimes they get too big that they cannot get their head back from out of their wing to break the shell which makes them unable to pip and they die that way. Safer to have lower humidity than very high humidity throughout.
By the way I have two incubators that have an automatic spray which I set for the humidity that I need and the eggs are turned every hour automatically as well. They contain three shelves each of 99 eggs or more so hold 300 eggs in each incubator.