Page duration - the time spent by a user on a page.
Install the package via npm:
npm install --save nr-page-duration
Be sure to require it in your code before compiling it:
Lastly, check out the data in Insights via a query similar to:
SELECT histogram(duration, 1200, 20) FROM PageAction WHERE actionName = 'PageDuration' SINCE 1 month ago
This will produce a graph similar to: