You should be able to work out the hatch dates, and it won't matter if they are hatching when you are not there, they hatch at different times and sometimes over a day or two,ocassionally longer.
Try to turn the temp down on the thermostat by a couple of degress for the last week, as the egg's produce there own heat as the snake/lizard moves around in preparation to hatch.
So if your incubating python egg's, say carpets then turn down from 90 degrees to 86-88.
Not everyone does this, but I have had great hatch rates in the past using this method.
What species are you going to incubate?
Neil