One of the best ways to preserve the romance in any relationship is to let your partner know how much you appreciate them. Do thoughtful things that let them know you are thinking of them. If you are married with kids have designated date nights when it is just you in a romantic setting. Show each other your love in practical ways by doing the chores the other hates. Never ever forget to tell the other how much you love them, often and sincerely. And always remember their likes and dislikes.
For example, my boyfriend knows I find it hard to wake up in the morning so he keeps some galaxy chocolate beside my bed because he knows once he points to it in the morning I will wake up. Funny I know, but very thoughtful and sweet too.