We have went back and forth on this and wanted to get some outside input.  I work for an online listing website that has classified ads on it.  These ads are generated by companies on our site advertising weekend events around the country. We have about 10,000 companies that use our service to generate their online ads. This means that we have thousands of pages being created each week. The ads have lots of content: pictures, sale descriptions, and company information. After the ads have expired, and the sale is no longer happening, we are currently placing the in the heads of each page. The content is not relative anymore since the ad has ended. The only value the content offers a searcher is the images (there are millions on expired ads) and the descriptions of the items for sale.  We currently are the leader in our industry and control most of the top spots on Google for our keywords. We have been worried about cluttering up the search results with pages of ads that are expired.  In our Moz account right now we currently have over 28k crawler warnings alerting us to the  being in the page heads of the expired ads. Seeing those warnings have made us nervous and second guessing what we are doing.

Does anybody have any thoughts on this? Should we continue with placing the  in the heads of the expired ads, or should we be allowing search engines to index the old pages.  I have seen websites with discontinued products keeping the products around so that individuals can look up past information. This is the closest thing have seen to our situation.

Any help or insight would be greatly appreciated!

-Matt