Google requesting really old urls. Housekeeping?

[lucy24]

Is google engaged in some kind of housecleaning venture? About ten days ago they suddenly started requesting URLs that were removed or redirected a long time ago-- in my case, three to four years. My redirect database covers exactly a month, so the change in behavior is really striking; it isn't the random spot-checking that they've always done. (It's also different from Bing's chronic rechecking, or the weird binge that Yandex has been on for the last month or two, now mercifully slacking off.)

I don't think it can be something strictly programmatic like "revisit this URL at intervals of exactly so-and-so long", because requests range all over the map. 3-4 years happens to be the oldest 301/410s I've got. Has anyone been seeing requests for really, really old URLs?

[netmeg]

I'm still getting requests for URLs from 2010 and before. I assume it's from old scraper links. Google never forgets.

[not2easy]

Periodically they seem to throw up old, long dead URLs as 404s. I waste time checking where they are "Linked From" but those are 404s as well, so I click it as "Fixed" and ignore them. Yes, there are more of them in the past 2 weeks, seeing URLs from 2009, 2010 and newer. I hope their self-driving cars don't use GPS data from 2009.

[RedBar]

Google never forgets.

And neither does Yandex, they're always trying old sites of mine that have been 301'd.