Your question is not cleared. You can set the time by clicking the Advance Segment > Goal Tab > Time on site. All features are available in the New Version.
Remember though that Google Analytics doesn't have any idea how long users spent on the last page of your site, because it's only invoked each pageload. Which is why pages with a 100% bounce rate have 0:00 avg time spent.
GA does it for you. But where di you get total spending time on your site, Google Analytics gives you only average time.