I haven't had school aged children but I have one child going to JK in Sept. and his baby sister is going to start at the daycare in his old space. I haven't asked his Mom yet, but it's crossed my mind that they may run into a problem for PD days and I won't have the room for him.
Remember our mantra - your daycare - your rules! Do what is best for you and fill your spaces the way that works out best for you. We have all learned the hard way that the families will take care of themselves first and drop us without a thought sometimes. Other times they want to stay forever, so if the family is a great one you will work it out, but if not, you know what to do.