Passionate love is intense attraction + ecstasy + idealization, with butterflies and heart palpitations and dopamine-rich brain regions lighting up — caudate nucleus and ventral tegmental area [1][2]. Early love elevates nerve growth factor (NGF) — then levels return to baseline 12-24 months later [1].
Companionate love is slower, steadier, built on stability and care. Theorists assumed passionate fades fast while companionate stays stable/increases — data is messier: both can decline equally over time [3][4].
Acevedo et al. 2020 "After the honeymoon" notes newlywed years are critical and predicts long-term satisfaction, with sharp declines linked to disillusionment, negative affect/conflict increase, and habituation [5].
~40% report high marital happiness over 20 years [5]
30-40% married 10+ years still report high romantic love [5]
Idealization early predicted less steep decline up to 13 years later [5]
Translation for you: Significance — making them feel seen, important, and chosen in ordinary moments — is what keeps landing after intensity fades.
Average honeymoon estimate: 18 months to 3 years (Tennov 1979) with serotonin/normalization around 12-18 months [4].
Companionate may decrease slowly over decades [4] — intentional responsiveness buffers that.