Ok this is all new to me, I here people all the time say when something goes broody they keep stuffing eggs under them.
Yes but the object of doing that is to make sure that all of the eggs are due to hatch at the same time. Turkeys and guineas are 28 days so all of those need to be under the hen at the time she starts sitting. If you want to add chicken eggs (21 days) add them 7 days after the hen starts sitting.
While it is not advisable to keep adding eggs every day to an incubator, a person can get away with doing that. The incubator isn't going to turn itself off because it thinks it has enough eggs hatched. The incubator isn't going to stop because it doesn't like the looks of a chick that hatched.
I have had turkeys decide that they had enough eggs hatched or were tired of their nests being disturbed quit sittiing and walk off with their hatched chicks leaving behind eggs that were days away from hatching.
Last year I had a hen hatch 8 of 11 eggs. She took her eight little darlings and hid them in the grass while she picked a fight with my dog (they were separated by a fence). While they were fighting I caught the poults and put them in the brooder. After a couple hours I finally broke up the turkey/dog fight. The hen wandered around for the next four hours looking for her chicks. She finally returned to the three eggs remaining in her nest after being off the nest for at least 6 hours. Two days later she came off of her nest again with 2 more chicks for a total of 10 out of 11 eggs hatched. Had I allowed her to keep the original 8 chicks she would not have returned to her nest to hatch out the last two poults.