No matter how many dozens of Netflix-and-chill nights you and your long-term partner have had together, there’s something that keeps you tuning in for more. But just as individuals age and change over time, the same goes for your sex life: What turned you on when you first made it Facebook official might not be the same for you now.Experts say that the key to a happy, fulfilling sex life with a long-term S.O. is changing things up and making your own new sex “rules” as you go along. But of course, these “rules” aren’t hard and fast, and they don’t stay stagnant; they grow and change with your relationship. Just as a casual relationship might progress to commitment (and, for some, children), your sex life can shift in tandem with your ever-shifting partnership.“In the beginning, everything is carefree and wonderful, and it's easy to have loving and sexual feelings towards your partner,” Sarah Schewitz , PsyD and licensed clinical psychologist, tells Refinery29. It’s what comes after that honeymoon phase — children, debt, and boredom, to name a few possibilities — that can put a damper on your sex life.That’s not to say that every single long-term couple has issues in the bedroom (in fact, there’s plenty of research out there that suggests that people can stay “very intensely in love” for decades). But studies suggest that couples who exhibit certain sexual behaviours tend to be more satisfied with their sex lives. And even if you’re already satisfied, putting effort into your sex life and learning new things can only be a good thing So what are some tips, tricks, experiments, and “rules” sex experts wish you’d include in your sex life? We talked to the experts themselves and rounded up 30. Try ’em or break ’em — just have fun.