There are different licenses available, some of which expire after 8 months, some of which expire after 12 months, some of which expire after a particular online course is done.
The online store only sells the license that is valid indefinitely, while you are a student enrolled in an appropriate degree-granting institution. You have to stop using it when you are no longer a student, but if you were to later start taking courses again you could start using it again.
The advantage of the Software Maintenance Service at extra cost is that you would get access to the newer software releases.
