I'm not saying every relationship becomes routine/boring/sour/whatever, but often the sorts of things listed in the article slowly disappear from a relationship because of outside stresses. And those little things are important...
EDIT: That first line seems really bitter, and it's not meant to be. I've been married for 12 years, and we've together for nearly 20. My wife and I still enjoy each other, but there are times that those stresses (work, school, kids, life) make you forget about those little things. If you can keep the "good nights" and "have a good days" going through the worst of times, you're in good shape.
It doesn't hurt to be reminded that each other's happiness is important, even if you think your relationship is as good as it can be. :)