When an assignment is created and linked to a class within Turnitin the default end date for a class is 6 months. If assignments within that class do not expire until after the default 6 months this will push the class end date out to the longest date out for an assignment.

The class can be extended by logging in through the TurnItIn software or you may add a new TurnItIn assignment through the course and this will also extend the active period on the course in TurnItIn.