What is the biggest differentiator between your customer segments? By that I mean, when you sort your customers what are the first big buckets? Gender? Age? Geographic Region? Income? If gender is the biggest differentiator, then what I’m going to say is very, very important.
You wouldn’t need a 25% increase in time on site to get Google to increase your page rank and send you more traffic, just a tiny advantage would do the trick. Google wants their customers, the people using the Google search engine, to be happy with their search results so customers don’t switch to another search engine. Google is going to reward sites that have a little extra something special with more traffic because it’s in their best interest to do so.