How long does passionate love last, and what takes its place?

Passionate love, the dizzy, can't-think-of-anything-else kind, does not stay at its peak for ever. Researchers give several estimates for how long it stays intense: 18 months to 3 years, 12 to 18 months, or only about a year. What takes its place, in many couples, is companionate love: the affection we feel for people whose lives are deeply entwined with ours, an emotional bond that takes some time to develop.

Robert Sternberg gave this a shape. His triangular theory says love has three components: intimacy, passion and commitment. Passion drives romance and desire, intimacy is closeness, and commitment is the decision to stay. Combine intimacy and commitment and you get what the theory calls companionate love, a long-term positive connection observed in long marriages where passion is no longer present.

But 'passion turns into companionate love' is a popular hypothesis, not a settled law. Other accounts say companionate love takes longer to develop but matters at the beginning too, and might sometimes come first. And passion does not always vanish: in some couples, romantic feelings have been shown to last longer, with fewer of the obsessional features.

There is a wry human footnote. Elaine Hatfield pointed out that people call a relationship 'romantic love' while it is going on and 'infatuation' once it has ended, so the difference may only be visible in hindsight. The honest answer to 'how long?' is therefore: often somewhere between one and three years at full intensity, then something calmer, but there is no fixed timer.