Need some Advice on this site…low PPC perfromance.

I have a site that has some small traffic.
It recieves about 8 -10 visitors daily.
The Average Visit Length is 13:48 (Thirteen minutes)
But some stay on for 20 minutes and even 1 hour.
Adsense is not performing at all on this site. I was wondering if anyone can advise me on Pop-Ups Pop-unders.
Since I’ve heard this pay by CPM and my visitors stay on the site for so long. I think this would perferm better.

Original post by Dollar