This was just what I was looking for--a way to automatically expire posts in advance. The expiration options are very well thought-out, and the one I use is an option I had never even considered until I saw the options available: the plugin lets you automatically move expired posts to another category. So, whenever I create a post in the "Announcements" category, I set an expiration date and the plugin moves them by default to the "Archived announcements" category. Moreover, the plugin is well integrated with the WordPress system, so that in the listing of all posts, an "Expires" column is added along with everything else. Fantastic all round!