netmeg - 4:17 pm on Aug 22, 2013 (gmt 0)
I run event sites (everyone knows what kind by now) and what I do with expired events depends on whether or not they are likely to recur.
I use living URLs from year to year, so after a recurring event expires, it disappears from all active navigation and taxonomy pages of the site, and a notice appears on the event page that the event has expired and we're awaiting the next update. But I do not noindex it. This is also what I do with recurring events where, say, this year's was cancelled.
If it's a one-time event, I just go in every now and then and delete 'em and let them 404.
Any location taxonomy pages are programmed to add a noindex tag (and remove the ads) if there are no active events on them.
So far that's worked out pretty well for me.