Where does love begin?
What do we know about love? It is this ethereal substance that we are in search of in our lives. It's mercurial. So days there seem to be more of it than others, but at the same time the more you try to hold it the faster it runs through your fingers. Rorschach doesn't believe American love exists anymore, and if Laurie and Dr. Manhattan are an example of American love then maybe it doesn't.
Love transcends time
We see Dr. Manhattan both find and lose love. He meets the love of his live as a man before he becomes a superhero. He is the perfect picture of success. He is the best in his field. He has a beautiful girlfriend, who is also amazing in her field. He has love, success, and a future. This is however, not how the story plays out. Love does not have such a simple path.
John is not destined to love easily. His humanity is taken from him, though this appetite for sex does not disappear. He is very much a man. He is very much human and yet he is constantly forced farther away from humanity. Even though all he really wants is to be loved and to help those he cares about feel loved.
Around and around we go
The same moment happens to Dr. Manhattan multiple times.
Dr. Manhattan exists both inside and outside of time. The biggest problem for Dr. Manhattan is that love is timeless only in a linear fashion. Dr. Manhattan is omnipresent, though not omnipotent. He doesn't know how to exist because he is a man thrust into the existence that is not human.
Where we stop nobody knows
Laurie and Dan are very human. They may be super, but they're not above the lust and angst that defines humanity. Laurie needs the things that Dan can give her, and she takes the things that Dr. Manhattan tried to give her. The love story started with Dr. Manhattan but is much more complicated and included multiple generations.
I love you to the moon and back
they can't disagree
or eat Indian food, or love each other...
Oh it's sweet. Being alive is os damn sweet.
Relationships and love are complicated. There is one common denominator that is necessary, however. You have to be alive. Perhaps you can argue that only one part of a relationship needs to have the essence of life, but that essence is necessary regardless. Laurie realizes this. Love and sex can be fleeting or they can last longer that the momentary glimpse that popular culture and are can give us, but the only way that we are able to see this is through time.