For me, I am more likely to hear about "soul mate" or "being completed" in my monogamous friends than in my poly friends. They are more likely to separate how you love from what love is.
I read a few Heinlein books. They are interesting in how they break through many social norms. However, I usually don't get pulled too deeply into his stories. The Heinlein quote that I do hear is "Love is that condition in which the happiness of another person is essential to your own." It doesn't quite reflect my view, but I like the concept of it.