That's why I hate staggered hatches, there are no good answers. Let's look at some of the issues.
Humidity is probably the easiest. It is still important. Over the incubation the goal is for the egg to lose enough moisture so the chick can hatch yet not lose so much it can't hatch. Luckily there is a fairly large window for moisture loss that works. Also, if the air inside the incubator is too dry when the chick pips the membrane around the chick can dry out and shrink. Shrink-wrapping doesn't happen all that often but it does happen. That's why you increase humidity during lockdown and it's recommended you do not open the incubator and let the moisture out.
The biggest risk of shrink-wrapping is after the egg has pipped. If your incubator is running warm the eggs can pip and hatch early, sometimes pipping more than two full days early. That's why you go into lockdown at 18 days, to get the early pippers. If your incubator is running cool hatch can be equally late. When they will actually pip is a great unknown. Also, I've had hatches of abut 20 chicks totally over within 16 hours of the first one hatching. I've also had hatches stretch into the third day after the first hatched. That just adds to the complexity. With the time difference in your eggs running the incubator fairly dry after the first hatch could be a good move to balance out the moisture loss.
There are other benefits, but the two primary reasons for turning is that turning helps keep the yolk and developing embryo from coming into contact with the inside of the porous shell where it can get stuck. If it gets stuck it won't hatch. Also, turning helps body parts form in the right places. With chicken eggs, by 14 days a membrane has formed around the chick to protect it from coming into contact with the inside of the shell. That's the same membrane that can dry out and shrink. Also, body parts have formed by then. After 14 days with chicken eggs turning isn't that important, you can stop. But early on it is important. With the time spacing you need to be turning your later eggs.
I don't know what your incubator or turner looks like. With mine I can remove some trays of egg holders, not all can do that. I remove my turner at lockdown. Even if it is turned off a chick could get a leg, wing, or neck caught in a sharp corner. I wan't to avoid that. When they hatch they make a mess. Goop from the hatch can get everywhere when they are crawling around plus they start pooping. Removing the turner makes clean-up easier.
The inside of the incubator is pretty moist and is at the perfect temperature for bacteria to grow. After thee days that goop and poop can start to stink pretty badly, I've had that happen. After the first hatch is over it is probably a real good idea to empty the incubator and give it a good cleaning. Don't worry too much about the eggs cooling off. As long as you don't get ridiculous on how long it takes to clean it won't hurt them. Wrap the eggs in a towel or such to hep insulate them. When you start the incubator backup use water about 100 F to help it warm up faster. Do not use hotter water, you don't want to cook the eggs.
When the first chicks hatch they crawl all over, including all over the unhatched eggs. That can get goop and poop on them. Not good, remember bacteria. If you can with your turner and incubator you might make some baskets out of hardware cloth (you can do that with bending) to reverse over the first eggs to hatch. That would keep them from crawling over the other eggs. Some people use those little plastic baskets fruit comes in. This basket idea can also help you keep breeds apart when they hatch.
If you can basket the eggs and create an opening in your turner for that, turning is easy. Otherwise you my have to open the incubator during lockdown to turn eggs. Maybe spritz the eggs with 100 degree F or less water to help stop them from drying out. Some people can turn eggs by sticking something through the air vent.
People that regularly do staggered hatches often use two incubators, one to incubate and done to lockdown and hatch. That takes care of all these issues.
These are the reasons I hate staggered hatches and don't do them. People do staggered hatches with one incubator and can be successful, even if they don't consider everything I said. These are the things that can cause problems, not that they always do. I wish you luck!
