I believe two types of relationships exist: Passionate and "Companionate"
I've noticed that these Passionate relationships (1) thrive on this phenomenon of "arousal" (which is an aggregate of feeling needed, infatuation, and a lack of intimacy), (2) are perceived as uncontrollable, (3)are sudden in onset, and brief in duration, (4) are ultimately influenced by one's cultural belief in love.
On the other hand, Companionate relationships (1) thrive on mutual trust, tolerance, and caring, (2) are controllable, (3) are slow in development, (4) are ultimately encompassed by mutuality of dependence and reciprocation of love.
From my observations, I have concluded that, ironically, successful relationships may lead to less passion.
Most people believe that physiological arousal in the presence of others is a key aspect of passionate love. The truth is that early in a relationship, a variety of emotions contribute to the perception of passion. Thus, uncertainties about the ultimate prospects for the relationship, anxiety over the spectre of rejection, joy over the reassurances of the other all contribute to the romantic experience.
Reduction of anxieties and uncertainties, senses of security and trust ultimately undermine passion. Successful partners become "meshed." They learn to accommodate to each other so that interaction sequences run off smoothly and serve the needs of both. Emotions are likely to fade in intensity as each partner successfully adapts to the other.
Ultimately, a couple may lose sight of the various ways they rely on the
relationship to satisfy their needs, taking each other more and more for granted. (One is less emotionally responsive to the benefits provided by the other as they become expected.) And, the degree to which the relationship is interdependent only becomes apparent by episodes of conflict or separation.
So, given the choice... I think I'll always prefer companionate relationships. "3," which would be some sort of conglomerate of the two (beginning as a passionate model then transitioning to a companionate model) seems like a waste of time. :-/