What an excellent post! SO and I have experienced this waning and waxing too, although we haven't talked about it outloud.
Longing, teasing, anticipation, surprise, change-ups are all tools in our long term R tool box to keep things fresh, as they say.
I know one of the things that really turns my SO on is seeing me in public (such as a party) interacting with others, and, to some degree, being desired by other men. I know that probably seems crass or a touch cromagnon, but we are, after all, "victims" of evolution. I think we can certainly play that to our advantaged! (said one venusian to another...)
Go! Flirt! Have an excellent time! And then go home and remind NG why you are, and always have been, the woman of his dreams!