I had a college roommate that did this a lot - he would lay in the bunk above me and take himself to the edge for at least an hour every night. Sometimes, he'd go ahead and cum, sometimes not. I never asked him if it increased his volume, but sometimes he'd have an awful mess to clean up, as evidenced by the wall behind his head.
I know that, in my experience, when I've gone to the edge, such as by watching porn, that when I finally DID cum, I shot a LOT!