The problem about allowing leeway is that if you say to yourself that a half-an-hour either way is okay, then one day you may think, "well, another half-an-hour won’t matter" then it may expand to more and more and more. Being an hour early or late one time wouldn’t cause much trouble, but doing it on a regular basis would be a bad habit. The discipline of regular meds is one your child will need to learn, and it’s much easier if it’s modeled by their parents.