The regular Student Suite license is not time limited. You can use it while you are enrolled in a degree-granting institution. (That does mean that when you stop being a student you have to stop using it -- but it also means that if later you go back to classes you could start using it again.)
There are Student licenses that are time limited. For example, a license that came as part of a MOOC is time limited. Also, if your Student license was supplied by your educational institution then it might be time limited.
Visit https://www.mathworks.com/mwaccount and click on your account, and on the page that comes up, click on "Install and Activate". On what comes up, look on the right hand side under the heading "RELATED TASKS". There will be a field "Expiration Date:". If it says "Not set" then your license is not time limited; if a date is given that that date is your limit.
