Did the clicks lead to sales? Absolutely.
User engagement is one of Google's many ranking factors so I believe my rankings are also benefiting from people sticking on the site longer. Also if Google analyzes my site for too many affiliate links, I'll be in the clear.
My other sites generally have people sticking around for just under 2 minutes.
Obviously this study isn't fool-proof and a variety of other factors could be at play as well, but the results seem significant enough to warrant a closer look as to how many affiliate links or ads your site should optimally have for ranking and for earnings.