My users love this hack! Thanks Kier, Kevin.
I have a suggestion for next version if you are entertaining any
1. Save the last used options in the database, so admin has to only change the date. If you have many forums, it can be tedeous, and might miss some of those private or test forums.
2. When the last run of emails is over, redirect back to panel, or change the submit button from "continue next xxx). Once you get used to clicking for next page, you migh send users in the last page twice.
Better yet, make it act like thread insed updates, where you set the max number of emails per run, and it'll go till done.