No. You can log-in and out as much as you like, as long as you finish the course within the allowable enrollment period. (60 days in most cases for continuing education courses) We post how long certain videos/activities will probably take and recommend you don't start a particular section/topic unless you have time to finish. For instance, if a video will take approximately 55 minutes and you only have 30 minutes before an appointment, it's probably best to wait until you have one hour of time before starting.