How you can limit the time in which participants access your academy
If participants should only receive access to your academy and courses for a limited period of time, this can be done via the activity status of the participant.
Navigate to the participant tab and select a participant. In the participant's profile, navigate to the right side of the profile to find the Status which will say: Will be blocked on or Unlocked on.
Status
a) active
If the status of the participant is labelled active, only the field Will be blocked on is shown in the participant profile. By clicking on the calendar symbol below this headline the date can be determined on which the account's access to the academy will be blocked.
From the selected date on, the participant loses access to your academy and therefore your courses, too.
b) blocked (gesperrt)
If the status of the participant shows gesperrt (blocked), only the field Unlocked on is shown in the participant's profile. By clicking on the calendar symbol below this heading the date can be determined on which the participant regains access to your academy. 
On the selected date, the participant receives access to your academy and courses (again).