You are not alone with this issue Lilian!  Our DW has about 1,200 pages each with their own content channels.  We also have hundreds of spaces each with their own channels.  Overall, we have about 275,000 items in our DW.  Over the past couple of years, we have reduced the items available to our search engine from the total 275,000 down to about 105,000.  That plus recommended results has greatly improved our user experience.  But, readers lose confidence in accuracy if they land on old content, so we are covering that as well.

This reduction is accomplished through several methods:

1. Archive rules
   • We have community rules for blogs (1 year after publish), calendar events (1 day after the event) and forum topics (90 days after the last comment)
   • We do not have community rules for wiki and folder content as we do not have a good way to draw a line in the sand that would make sense for all use cases.
   • We have encouraged our community managers to apply archive rules to their wiki and folder channels where it makes sense, but that has not been widely adopted.
2. Deleting pages/space/content
   • We are selective in what we delete as we have had several occasions of deleting, then after 30 days someone wants it back and it is no longer retrievable. But we do delete when we are confident we will not need it going forward.
3. Moving items to the Attic (this was our resolution to not delete things we may need to restore or refer to in the future)
   • As our site evolves and a page/space/channel is no longer relevant, we move it to the Attic, remove all permissions, and archive all of the content.
   • Only our admin team and a few community managers have access to the attic for reference/retrieval purposes.
4. Content Audit
   • We have more than 500 people that manage pages/spaces/content across our DW.  Wrangling this large group to actually do their content audit is very difficult.  Last year we started a program for each area of our DW to have a lead community manager to oversee the content audit process within their area.  Some have done better than others and we still have a ways to go to get everyone to fully complete their audit and on board with their maintenance program.
   • I provide the lead for each area their content audit report every three months.  The report is the full content audit report for their area, but I also provide them with a summary of what they really need to pay attention to for their content audit. Namely, their wiki and folder content that has not been modified for more than a year.  Their action over the next three months is to work with the content owners of that wiki and folder content to decide if it is still relevant and accurate.  For folder content that is still relevant, no other action is taken (but really, do you need to keep a briefing from a team meeting from more than a year ago active and easily found?).  For wiki, we ask them to review and edit as needed, but even if there are no edits needed, I ask them to edit and publish just to update the modified date.  This removes it from their next three reports and gives readers of the content confidence that it is accurate content.

I don't disagree that it would be helpful to have more automated tools, workflow and reporting around this topic built in because dealing with the dispersed volume is cumbersome and time consuming.  But I feel like all I've done over the last couple of years has helped tremendously!

I hope this is helpful for you and I'd be happy to discuss.  Just let me know if you'd like to and we can get a time on the calendar.