Hi @Batu2, thanks for writing!
The subscription is good for a total of four years, but it requires that you re-enroll into the program every 12 months. A kind of check to make sure that you are still indeed a student. When your subscription is about to end simply visit the student discount page and subscribe to it again. No need to cancel your existing subscription to do so. Please don't hesitate to let me know if you have any other questions or concerns 🙂