When charging a fixed amount or offering your course for FREE you can limit the amount of time students have access to course content after they have registered.
When adding a price to your course set the Student Access control to: Expires after a specified time period. Then set an amount of time from registration after which student access should expire.
The default setting for Student Access is: No time limit. This means a student will have access for the life of the course (as long as the website is online and they have paid or registered).
Please note: With subscription pricing there is not currently a way set a time limit on access. In this case a student will have access to the course as long as their subscription is paid to date.