I wrestled with sex drive disparity over the course of many relationships. In some ways, I still wrestle with it. Being in poly or mono relationships doesn't change that. It's a matter of regulating what I want or need, what a partner or partners can provide, and how to handle the difference (handle being rather important).
That said, it the way you write, it seems to me like you're in a bit of a mono/poly limbo. I took me years to accept my poly nature though I had a history of poly relationships since my early adulthood. You seem to be stuck between mono programming and poly emotions, and it's not clear if this is you shedding programming or trying on the emotions.
NRE is something that happens regardless of whether a relationship is mono or poly and can happen even with platonic relationships. Just like how life can get in the way of living, it comes down to how you handle what resources you have and how you manage your time.