The solution to this is actually quite easy: Start performing poorly in bed. Jizz as fast as you possibly can. Think about the bills while she rides you so that you get limp dick. When enough time passes, she will become more sexually frustrated. That is your cue to encourage her that it is time for her to get her rocks off from a black man sporting a massive cock. My guess is that if you start all of this now, you will watch your girl get deep balled by June of next year.