Everyone knows monogamy's weaknesses: same partner, no other partners to experience sex with, the loss of enjoying the unique little strengths that given lovers will have in bed for you or when you do things to them. However, it's very helpful to be aware of monogamy's strengths. Ones that are under-utilized by most.
The first strength is housed within what most consider to be its biggest shortfall: you only get to have sex with one person. What I discovered while I was single was the biggest disadvantage to having multiple partners who you see when your schedules permit: every time you have hot sex dripping with the novelty that our brains love, you often go to the sex methods and moves that the two of you are good at because you're hungering for each other due to the separation the two of you experience while you're apart and so you go to the favorite tracks, so to speak.
Discovering new sex things to do together is always possible, but if you want to do something with them that's more advanced and requires practice time, working on that doesn't get done due to the afore mentioned conditions. The different body and unique details are fun, but it is harder to grow and develop your sex life together.
The opposite is true for monogamous couples. Especially the ones that live together: Because you're together all the time and have much more sexual access to one another. This is where the brain will start to whine for novelty a bit louder and a good answer to that pang comes in the form of spending more time practicing sex together to get better at your sexual skills and refining your communication to give you unique experiences and the orgasms to go with them.
Every sex session you have with your partner doesn't have to be "flow sex" as it has been called. With more time together you can choose to have "training sex" sessions that are fun and hot in a different kind of way. Hot often at the precise moment when it goes from experimentation and forming the experience to the experience working and feeling and/or looking and sounding incredible.
In time you can develop a sexy anticipation of that eureka moment that is part of the uniquely adult wonder of a more sophisticated approach to a shared sex life. Because that's what monogamy is. A shared life. The decisions the two of you make about your sex life profoundly affect the other because there is no leaving to go to someone else. The concept of two becoming one in marriage proceedings is quite accurate in this case, so be aware of this when making decisions together about your one sex life together.