This article discusses Sternberg's triangular theory of love and then compares it to other theories that have been developed over the years. His theory says that there are three points to love (or the triangle) which are intimacy, compassion, and commitment. He says that all relationships evolve in the same way, that couples experience the same "stages" of love as their relationship matures.
While the triangle offers some insight as to how and why humans experience love the way they do, I don't know if I believe that something as complex as love can be boiled down to a formula. Love is such a multi-faceted thing and can be defined in a thousand different ways, that to say that there are only three main components is kind of ridiculous. It is easy to categorize people by the state of their relationship, but declaring that you can predict what will happen to them based on a generic calculation is a stretch. There are obviously patterns in every relationship; initial attraction, physical interaction, declaration of love, etc. but these things do not always happen sequentially like Sternberg suggests.
However I do agree with some aspects of the triangle, such as the six combinations of love that can stem from the three main points. These seem viable, as there are only so many ways to describe the state of a relationship. Overall, I think Sternbergs triangle is a dated method of defining love and its variables, however it still offers some insight and a basis to start thinking about and understanding these concepts.