Are you systematically re-directing all the landing pages that you're unapproving/archiving? Do you create a redirect to another Marketo page or to generic website pages? (e.g. if you unapprove a landing page on a white paper, do you redirect to another similar white paper or to the white paper library)? Are you keeping the redirect-rules forever or do you delete them after x period of time?
Cécile @ Talend