Actually, you didn't put a "today" in the I love my T thread, so the choices are pure, undying, constant love or temporary, 24 hour hate.
I wonder, how much of the cycling is just normal human? While I can't say that I ever "hate" my wife, there is some ebb and flow in my feelings about how great she is. Sometimes she is a little bit great, sometimes she is a lot great, on occasion I think I could live without her. With friends, there are times of greater or lesser closeness.
So for me I wonder, is the love-hate cycling unique to T's, or do we cycle (to a greater or lesser extent, or the same) with our other relationships? For me, the answer to that question is that I think my T relationship of about 18 months is probably a little less cyclical than my other relationships. It is more of a constant positive regard than my other relationships, although in general I would say that I am pretty steady in all my r'ships. There is rarely any drama.