Back in November 2012, I posted a thread on the same topic. I have taken one of my site and updated 1/4 of its content and the results were fantastic not only for these pages but for the overall site's ranking.Actually, the traffic was doubled within 3 months.
Read the discussion here - [webmasterworld.com...]
P.S. - I haven't changes URLs. That might be the difference between JS_Harris case and mine.