Hi Olli,
Not sure... we are new to this too...
We have recompletion set to send a reminder notification out after the user has completed the previous assessment.
Eg... the user has completed a quiz then the re-engagement email is sent after a delay. (48 weeks)
In the image below... you can see the last access and notification times ... even for users who have not completed the expected activity.
The activity trigger is controlled by the "Restrict access" setting.
I believe the "Activity completion" settings help control the notification time for inactive users.
Recompletion then strips out the grade with its notification email and the whole process starts again.
Dan may be able to confirm for us if he sees this posing.
cheers
Mark