Been there, done that, but I lasted more than 15 seconds, the pussy DP on the other hand made me cum instantly and hard when I felt my buddy flood the pussy with his cum!!
DVP is sensory overload. I've done it several times and thought I was getting comfortable enough with it that I could last and control myself but just a few months ago I met with a swinger couple who wanted to use me as a donor and have a bit of fun getting her pregnant. It wasn't but 5 seconds after I slid in along with her hubby that I was spraying sperm in her. I think it was the extra layer of her ovulating that made it unbearable to contain my load.