What effect do completions dates have on the learner?

When setting a completion date for a course or learning path, is the learner still able to complete the course/path past that date or are they prevented from doing that? Is that a setting we have to choose--whether or not they are allowed to keep working past the completion date? How does this work for learning plans where the number of days to complete is set? What happens when the number of days is reached? Are learners allowed to only view the courses/path or can they actually keep working and complete it? Can they be prevented from continuing past the date?