You can set the reminder to pop up at any time, 2 hours before, 1 hour before, 5 minutes before. But if you do not dismiss that reminder it will sit there until you get back and as the time closes/passes the actual time of the event, it will change into overdue. Often times you will see an overdue reminder when you first open Outlook up for the day/week and you didn't have it open at all during the course of multiple events, those events will then pop up as overdue.
If you are utilizing Outlook all the time and dismiss reminders when you see them and before attending the event, you should never see an overdue reminder.