Cheating on someone is breaking a promise, if was your spouse or just a SO. When you entered that relationship you promised that you will only be with each other. If one decides to cheat on the other that is breaking that promise and in my opinion is grounds for breaking that relationship. Maturity is basically abstaining from impulses to the best of your ability and using reason to guide your life not instict. Children are not mature because they use more impulses than reason. And most people are never mature even when they are 80 years old because maturity is not dependent on age but intelligence capacity and responsibility.
And if there is a problem in the bed you address it like any other problem. Your brother has a drinking problem? Oh lets just do nothing about it, it will solve itself. Any problem should be addressed directly. And if you are fetishes for Asians or Big butts, then find yourself a women with those charateristics. And when you want to explore the buffet, don't because you already have a plate full and you can go back when you have finished that meal first. Attraction is the initially pulls you in, like the lights of a casino, but it is the personality that keeps you there.
In humans, sex is the highest form of intimacy. When a human has an orgasm the body releases a hormone, oxytocin. This the same hormone release at child birth and during breast feeding. Now you cannot deny the bond between a mother and her child. For now the best we can do is sex for intimacy. It is a physical bonding between to people, and until we can go into each others sex is love.