tedster - 4:25 am on Mar 16, 2013 (gmt 0)
I work with one site that definitely has the kind of situation you describe - and we do nothing to articles as they age. Even after they stop getting search traffic, we just leave them untouched and the site is THRIVING in Google Search. So I'm not sure there really is any problem to solve, here.
Some people set up an "archive" folder and move old content there after a good while. I only ever did that once, many years ago, when the alternative given by the owners was just to delete the pages. The site still lost traffic for many months.