I think the fluttering love is what you get when both of you understand the concept of LLs, when you have the proper communication tools and when both of you have your wants fulfilled by the other person. Love is a choice after all and it's easy to keep going in a situation like that.
However, I think it is somewhat rare. It is so hard to keep it going when you have kids, jobs, stress, chores and so on. 50% of the first marriages end in divorces and I'm sure there are more mediocre marriages in that remaining 50% where people just accept and live their lives together. After BD I've been watching others and I don't see THAT many couples who are "limerent" like that after years. Ultimately, I think achieving it requires two people who have done a massive amount of self-reflect and relationship learning. We are all going towards that
In my thirties, BDd 2017, divorced 2 young kids new relationship