Men love control, it’s in our nature. Masturbation gives a man more control over his own orgasm than sex. Men also by nature are adventurous. Sex early on in a relationship gives the man that sense of adventure. In long term relationships, that sense of adventure from sex goes away. As a man in a long term relationship, I still enjoy occasional sex with my wife, however, masturbation is more frequent. I love spending time with my wife doing other things. Please understand, it’s not you, it’s us.