We have http://news.ycombinator.com/classic which, if I understand it, is for anything voted up or submitted by an account that is one year old or older. That was put in place, I think, to make a better home page due to the submissions/voting influx of new accounts a few years ago.
Now that it's been a few years since the launch of /classic (which is what I use as my home page), I think it's clear that today's /classic and the /classic of two years ago are very different. Today's /classic is almost identical to http://news.ycombinator.com/. What about adding in a http://news.ycombinator.com/classic2 (or making it a parameterized option) so that we can see stories voted up/submitted by accounts 3+ years old?
That would fairly easily allow us to compare relative activity and quality at any userbase age.