As of this release we change the calculation for page duration & session duration, so that you get even more precise data.
Until now, the page duration was calculated by comparing the timestamps of a page and its subsequent page. The difference between the two timestamps is page duration. For the session duration, the same logic is applied to all pages during a session. For the last page of a session, a constant value was being used (30 seconds by default).
With this new release, the actions and media requests are taken into account when calculating the session duration and the page duration of the previous page. Instead of just adding a constant value, event and media requests on the previous page are being used to calculate the last page duration.