In long term relationships, like long term marriages, feelings wax and wane.
True. And attachment can wane too, once feelings wane for a good while. Although I think attachment is what keeps people together, even contently, even when true feelings honestly have waned from yesteryear.
your partner can seem like the most annoying person on the planet and the next week (day month year, etc) you can be overcome by such a feeling of love that you wonder why you ever doubted your devotion to one another. YMMV
Well, if that went from week-to-week, I'd tell them to put their bottle down too. ;) But I agree with what you're saying. They can go up and down to a good degree, over time. We may not want to believe that to be really true, or to say it to others, but it is true.