I'm assuming that to use GL as corporate website/portal the topics and stories would represent the content for the site.
Content that has "expirations" may include: Product Promotions (involving offers that expire on a certain date) Event Descriptions and Notices (I know that this crosses into the Calendar function) News (that should be archived or moved "off the front page")In general, it's easier to set an expiration date when the content is being created rather than having outdated material remain on your site. (This is also related to a company's Records Managment policy but that's probably taking it a little too far.)