OK you know how they say with public opinion polls, one shouldn't look at specific poll results, but a trend, a string of poll results over longer periods of time?
it's kind of like that, for me at least
When i become infatuated with someone (romantic or otherwise), i tend to be very deeply infatuated with someone. I spend a great deal of my time thinking about them, talking with them, being with them...some days these feelings actually vary, like you've described above.
but over stretches of time these feelings endure but they also...settle, almost. the "spark" isn't lost, it just settles, as opposed to "crashes". When that happens i move on and start the cycle all over again once i stumble upon the next engaging person.
Very ADHD of me, i know it sounds pretty bad when it's all written out like this, but it's not that i just drop the person and forget about them, no...it's just the nature of that "connection" NFs seem to talk an awful lot about desiring. Some are short, but very intense..while others seem to just be made to endure regardless of what might come along.
If the connection was something more to me than just an intense infatuation, it would continue to hold my attention regardless of what other options came around, I've found.