I think Rhia Wieclawek did a great job explaining all the functionality you'll be able to get with out of the box reminders (she's an Avenger too). Check out Andrew Glasser second answer on this post that utilizes a site workflow on a schedule, to pull off sending reminders. I'm thinking you could do something similar to this, but modified based on your requirements: Send notification every 14 days if review not completed You'd have to query the due date and the status and then send your own reminders based on that.
Hope that helps,
Great - let us know how that goes & if you need any more input! In the mean time if you've found that an answer here helped you out, please mark it as correct.