Saying I love you for the first time isn’t about what’s come before. I think that’s why people are scared to say it. They think they need a quantifiable amount of — what? shared experiences? smiles? mornings waking up with limbs tangled together? — in order to deserve the word.
I think I love you means something else. It means that, yes, the past was good, and you have affection for that person, but when you say it, it’s about the future. It means you want more of those mornings and that your love will continue to grow, because you never stop falling in love.
When I’m 80, I want to say “I love you” and mean “I’m not finished loving you and I never will be”.