If you're a spouse who rarely says I love you, believing that your actions speak for themselves, preferring that behaviors do your talking -- consider changing it up now and then by using those three words.
On the other hand, if you're a spouse who says I love you all the time, such that it feels more like a habit -- one without thought or content, try expressing those three words with additional words of explanation and as well, letting a nice behavior do your talking at times.