The two questions of long-term romantic love of are polarity and unity.

The essence of polarity is being in awe at how wonderful the difference is between you two. If you've been married a few decades, the sign of polarity is that you continue to fuck.

The essence of unity is implicit trust the other person wants what's best for you. If you've been married a few decades, the sign of unity is having a single bank account with no his/hers accounting.

That's the essence of a long-term healthy marriage: fucking and having a single bank account and having no intention that it be otherwise.