But it is very easy to turn that into an oversimplified conclusion: “A new partner is exciting; an old partner becomes boring.”
In reality, the person does not have to be the new part.
A new activity together, a trip, an unfamiliar place, a new social environment, an unexpected side of your partner or an experience that takes both of you outside your usual roles can also create freshness.
Research on so-called self-expanding activities has found an interesting association: couples who engaged in new activities that broadened their shared experience also reported greater sexual desire and relationship satisfaction.
That is not a prescription saying, “Take a climbing class and your sex life will become amazing.” Causality and individual differences matter.
But the underlying idea is interesting. In a long-term relationship, one enemy of curiosity may not be the familiar partner themselves, but the conviction:
“I already know everything about this person.”
Usually, that is not actually true.
Sometimes novelty is not about finding a new person. It is about discovering something new in someone familiar.