What happens in a workflow (editor) flow when an "approval - user" activity passes due date?

[Beowulf]

Hello - I really tried to find the answer to this question, and I am a little surprised that I was unable to, so please accept my apologies in advance if this is an obvious question. 

I am trying to build a workflow in the classic Editor (business has not vetted Studio yet, so I'm constrained in this regard).

SIMPLIFIED USE CASE: The goal is to have an app that kicks off a notification at defined intervals relative to the "expiration date" field on each given record. If it matters, the intervals are 90, 60, 30, 2, 1,0 days to expiration. The user is expected to acknowledge the notification, at which point no further notifications should fire.

QUESTION

•  In the workflow activity "Approval - User" there is a schedule at the bottom of the config screen. 
•  According to what I've been able to find so far, this is where I would define the logic to set the due date of the task. 

1.  What happens when a due date passes, i.e., the Approval is overdue?
2.  Is there a way (business rule, script, something else) that could be used to tell the workflow what to do in case a given approval is overdue, e.g., email the manager of someone named in a field on the underlying table record? 

[Brian Lancaster]

I could not find anything on that either. I have been using workflow for years and I have never used the schedule section. In DOCs I found an article about the Approval - User but it gives me that same info that displays in the scheduled section.

My only suggestion would be to test it by setting the duration to 1 minute and see that happens when that expires.

[Beowulf]

Trial and error was my plan as it is, I'm just glad that I'm not missing something obvious in the docs

Thanks for you reply.