I find that for the 2nd or 3rd SOG in a day I sometimes run out of fluid. In that case either I can bang away endlessly without cumming, or when I do cum, it isn't as much fun as the first SOG. I'd love to hear about some diet or technique that would enable me to produce on the 2nd, 3rd, etc., SOG.
Being able to bang away forever without cumming is not as much fun for the chick as you might think. First, it leaves her feeling inadequate at the end if she doesn't make me cum. Second, at some point, it stops feeling good. I've actually faked it on the 2nd or 3rd SOG a few times just to make it a more enjoyable experience for her.
I doubt very much things like viagra would help me because getting hard isn't my problem, it's having enough fluid to have a satisfying finish that challenges me sometimes.