Do events in the Outline age off?

I don't believe they do. I will do some digging and testing playing with dates and see if i can find out.

Grouping may also have an affect on items displayed if on entry contains a number of items. Common with photo uploads.

This was actually from a Dolphin site.  The owner asked me to see why the outline was not displaying on the home page.  I don't know if the owner meant the entire block or just the content of the block.  When I looked at the site, the outline block was displayed and there were three events listed.  Clicking on More loaded more events.  The settings in the backend was to show 10 events on the Homepage.  So that brought to mind if the events would age off and thus if no one was posting content that would be in the outline then there would be none.  However, there are no settings in the backend for ageing for the outline block.