I have been thinking about this a lot lately. Say your partner is completely content with your sex life. What would be the incentive or your motivation to try new kinks and foreplay things that they bring up interest in ? This is assuming you have really no interest in the things brought up. More frequency or really to change anything? Would it be so that the other person does not cheat? Because if you're having as much or more sex than you desire seems that you would just have no motivation to change anything. You do not do the things the other partner wants, and you still have as much sex as you want.