I'm doing this because Wordpress won't accomodate a site with this many pages - technical issues with the CMS. I was going to move CMS so I can still admin my site, then figured what the heck, for now I'll dump the content and stick to my core money pages.
The pages are part of a linkbait project to drive links to my homepage, and I'm not looking for more links right now. There's likely no links to those 5K pages.
The pages do get traffic, but nothing that monetizes. In fact the traffic to those pages generates plenty of service calls that are related to my niche but non-buying customers. I try to look after those folks, but if they're not calling me anymore that's fine too. At one time I had believed that 5000 pages of long tail terms would help - but it hasn't from a buying traffic perspective. I still get almost all of my money traffic from a short list of search terms.
I think the test will be if the more focused page rank matters more, or the additional content matters more. I don't know enough to say either way...but it should be interesting.