Hi Cindy,
Based only on the last two years experience, the female will stay in / near the box for 6 to 8 weeks. Once the owlets fledge, it is just a matter of days until they are out'a site until next year.
The male is also typically within eyesight of the box while Mom is inside. They are so camouflaged that it can be really difficult to spot them. We only learned where Dad likes to watch from by seeing Mom come out & look his way & call for him.
It has been a true joy to watch them and has more than paid for itself in entertainment value.
They are very regular, so if you observe, you will learn with both come & go and can just about guarantee that you can see them daily - both perched & flying in & out. I would do it again in a heartbeat.
At least in our area, they show up in December/January and stay till Feb / March.