Each page has an owner, a contact, and an expiry date. Owner is responsible for keeping it up to date, and if you see a page that is expired you can ping the owner (unfortunately we don't have "alert on expired page" yet). If the owner is unavailable, the backup should be able to answer any queries/update the page, and if they can't then the failure of that lies on the page owner. There are a few pages that have empty backups, by virtue of our company size, but all the critical stuff has an owner, backup and is checked once every month or two.