Every course will hold a permanent record of completion for the user. Certifications will track each successive completion of the course depending on the timeframe allowed to renew the certification. The Editing Trainer has the ability to control how a course completion is calculated. There should be planning that goes into the completion before you open the course to your learners.
Each course has 7 different variables that you can modify and combine to determine whether a user has successfully completed the work required to get credit for the course. Once the course has students enrolled, changing the requirements can affect previous learners and can even remove their completion record altogether. Care should be taken to avoid that, if at all possible.