We will be celebrating our 30th this year. When I told that to a neighbor she said, "you're just getting started. We've been married for 75 years."
A couple were celebrating their 50th wedding annivesary. The wife, congratulated on her successful marriage, replied, "successful? It's not over yet." IOW, things could still go wrong.
I long ago came to the conclusion that "falling in love"or being "in love" is just a euphemism for infatuation. They are the same thing. They only vary in degrees of intensity. Both are chemical reactions in the brain. I once read about the chemistry of love. And as the OP mentioned, it does have a vital purpose to society. It gets two people together long enough to produce and raise offspring. Our society celebrates being in love as though it were really love (and not just intense infatuation). The movies depict, the songs praise it. They speak of the "feeling" as in the feeling is gone, etc. Or, I love you but I'm not in love with you. Whenever we speak of love as a feeling, we are speaking of infatuation--brain chemistry--and, like other drugs, it can be quite addicting. It feels so good.
Love--real love--is not a feeling. It can be felt but is not itself a feeling. I compare it to the sun. You can feel the warmth of the sun but the sun is not, itself, a feeling. To me, true love or real love is when you wake up next to that smelly person lying in the bed next to you and think, "what did I ever see in him (her)" and you decide to stay anyway. You decide to honor your vows and you decide to behave in a kind and supportive way when you really want to tell him to take his ugly recliner ideas and go away. Or when he decides to be nice when he really can't see the difference between this chair and that one and he thinks you are being ridiculous.
Love is a choice and a behavior. Infatuation is a feeling based on chemicals and brain chemistry can change.
Of course, if you choose real love and you choose to make it through the lows you will be rewarded with fresh waves of infatuation (that feel good feeling we all love) from time to time. Just don't give up when they ebb. It's like the ocean, those feelings come and go and I would not want to base a relationship solely on them.