Some folks say to wait until they are all hatched and dry. Others reach in occasionally and grab the dry ones, and the empty shells occasionally, perhaps adding a wet paper towel to keep the humidity up. Last spring, I had my incubator opened a number of times during "lock down" due to temp issues, and still had a wonderful hatch.
I can open mine all the time with no issues. The little table top ones are harder to keep heat and humidity so you are better off staying OUT of it.