I say it quite a few times each day too, and try to say it in different contexts, so it doesn't just become the "ending to a sentence or a behaviour" if you know what I mean. Sometimes I'll sit one of them down over a snack and look them in the eyes and tell them everything about them that I'm proud of and then tell them they're very special and unique and that I love them very much. Both of my kids will randomly come up to me or DH and say, "I love you sooooooo much." (usually with an accompanying huggle, as DD calls it, or a love slap from DS).