Of the stats packages provided in cPanel, AWStats will give you the best length-of-stay data.
Even so, it is only marginally helpful. It is not specific on a per-page basis, so if you have multiple pages on your site, you won't know which pages have long visits and which pages have short visits.
If you
really want to know what's going on on your site, get hooked up with
Google Analytics. It's free, and it will help paint a phenomenal picture for you, day-by-day, visitor-by-visitor, referrer-by-referrer, or by any number of other variables.

Bailey