Students are not removed from D2L once they graduate. In addition to D2L, students retain access to Campus Connect. Students will use the same login credentials for D2L and Campus Connect, and may need to reset their Campus Connect password to login.
Courses may not be available after a certain time has passed, however, as eventually courses are purged from the system. The records and retention policy related to instructor materials (including D2L course materials) can be found here.