Eric - the edit button is there for 30 minutes after the INITIAL post. 
Example - at 12:30 you entered/posted a reply.  You have 30 minutes from that time to change it all you want.  At 1:00 you can no longer edit anything.  The clock does not reset upon any further edits/changes.

Now - I checked the link you provided - thanks!  I'm of the mindset to make my own if it'll save me $.