I Love you to me is very serious and I don't throw it around much at all. My DH on the other hand tells me he loves me constantly....like every 5 minutes we are in the same room together. I love him more than life as well I just don't say the words as often as he does. I guess everyone has their own opinion of what you should say or do to express your love. To me its snuggling, hugging, holding hands etc. I guess I don't feel like I have to say I love you for him to know I love him.
He on the other hand says it constantly along with everything else. I don't think I would have ever been comfortable saying I love you unless I was sure he felt the same way....but he said it first and I returned it, of course we were only 15 at the time and it took a really long time for both of us to realize that it was really love.