RSS Board says to use Dublin Core's dcterms:valid in their MRSS spec: http://www.rssboard.org/media-rss

To hide an article you expire it right away. Numerous video platforms support this tag (youtube, thePlatform, dailymotion).

http://dublincore.org/documents/dcmi-terms/

I'm not sure why it isnt in the RSS spec, but I wonder if any CMS's still support it in the text world.