In the culture of today, it is rarer to find a couple who have been married for many, many years than it is to find ones who have been divorced and remarried several times. It is even rarer to find a long lasting married couple who still love each other. I am of the opinion that the death of romance in a marriage has an awful lot to do with that.
So, what kills romance:
When he doesn't want to hold her hand walking down the street.
When he compliments his mother on her new dress and compliments his wife on the new cleaner she has bought.
When he buys his mother flowers but never buys them for his wife.
When Valentine's Day becomes something for courting couples.
When after thirty odd years together he still has no idea about his wife's taste in anything.
When, knowing that she is passionately against killing anything for any reason, he buys her a mock Victorian ornament containing a dead butterfly as part of the display.
When she asks him to buy her some knickers while he is out shopping and he comes back with the sort his grannie would wear.
When he comes home and sees his wife has been crying, and says: "what've you got to eat?"
When she asks him specifically to keep a secret and he goes about telling everybody.
When, at a company dinner and dance, he makes a point of dragging her about and introducing her to absolutely everybody, with the exception of one woman who comes to sit nearby. She assumes he doesn't know her, but when she returns from the loo she finds them dancing together. He must think she was born yesterday!
I am sure I can think of some more, but if you know of any, please feel free to comment.