netmeg - 6:45 pm on Feb 18, 2013 (gmt 0)
I have to do it on a by site / by page basis.
I just purged a ton of old blog posts from some event sites, because they weren't relevant to my current content. They never really get any links anyway (the events do) and the information out of date (and a distraction), so there were more reasons to get rid of them than there were to keep them.
Most of my events recur; I purge events if I know there's a reasonably good chance they were one-time-only, or have been canceled for good. I will redirect to another event or the location of the event if I have some reasonable alternative to send people to.
Most of my best links go to my home pages or my taxonomy pages, and they're not going anywhere anyway.
On my blog site, I could see removing old posts that weren't relevant, or repurposing them into something worthwhile. I don't post often enough for it to be an issue. Yet.
I'm about to go through and purge a client blog mostly because the primary author (and now ex-employee) was a horrible writer, and the client doesn't want most of that content representing his company. I'll rewrite anything useful (or contract it out) and just stuff the rest.
(By the way, I never throw anything *away* - I just move it out of the way.)