I've had both monogamous and non-monogamous relationships encompassing a range of configurations over the years. I believe that there's a spectrum of mono and poly tendencies, just like with the Kinsey scale, and that for the folks in the middle portions of the range it's all about choice -- what's right for you and your partner(s). See my signature line for my current situation.
Something valuable I've learned?
Time creates change. If something isn't right for you now, that doesn't mean it won't ever be. If there's something you can't say or something you can't do now, that doesn't mean it'll always be that way. Some things are stable enough so as to be functionally immutable, yes, but most aren't. And active stretching and flexing and *trying* to change when you want to make change is very important, no doubt. But, but. Sometimes patience and time are what's really needed. Sometimes you just need to sit with a concept and see where you end up. Time creates change, on every level, in all of us, and we would all do well to be aware and respectful of that fact, to allow space for it, and to not feel betrayed by it but rather work with it and embrace it.