My atiel fertile egg laying process? HELP :)?

My male and female atiels recently conceived an egg 3 days ago and the other yesterday. I am just uncertain of why they are not in the nesting box all the time to incubate their eggs. Whenever i open the cage both of them come out of the nesting box or cage and play with me. But sometimes one goes in to sit on the eggs. will the baby birds die in the egg if their parents are not constantly incubating them?