
That's okay, Linda. My perspective of it goes a little like this

~
"Long ago" suggests they've been together quite awhile, much longer than either had planned or thought it would last. "We agreed to keep it light" ~ what people 'agree to' certainly isn't what it always ends up being. Going to the other end of the continuum, people "agree to" what they say in their wedding vows. We all know the rate there. I've seen where one-night stands have metamorphed into permanent relationships. Agreeing to "keep it light" could have been an insulation against pain, hurt, rejection, when you [knowing the odds against you] pair up with someone, with whom the likelihood is that it won't work]. Can't tell you without checking ~ well, knowing the incubation period of Leonard's songs, it really wouldn't do any good, anyway ~ how long ago the song was written, and how it aligns with Leonard's relationship with Rebecca.
However, for my purposes, I can use the two of them as an example to make my point. She's the much younger, charming, beautiful actress. He's a much older, profound, charming mentor-type poet. A long-term pairing wouldn't necessarily be a 'given' in either of their thinking. She might go off with a younger man. He might go off with another woman. Despite her beauty, her intelligence, and her charm, it remains a given that he is highly desirable, and may go off, either to another ~ or simply on his own, also a pattern in his life. However, they're certainly loving and enjoying each other for the moment. So, they insulate themselves emotionally with, "Let's just keep it light." "Yes, okay. I think you're right." I can easily see an "Annie Hall" dialogue, with each of their thoughts projected above their heads during the course of it.
Their relationship works well.....far better than either truly expected, or dared hope for, and their relationship settles into more of a marital connection, as they live together, set and achieve goals, plan ahead, enjoy the moment, and become a
real part of each other's lives. Eventually, sadly, their relationship slowly begins to metamorph in other directions.
She may have become depressed or sad about something. Or, she may have been that, when she first entered his life, with her still wanting to "keep it light" [I think of someone in the emotional state of Janis Joplin, when I look at it in this way] His gratitude of these times together, and his 'older' perspective may have helped her through this time. He was there for her. She learned to 'walk on air' as a result of her acquired belief in herself, brought about through him. He knew things were going to turn out fine for her, and was able to successfully encourage her in that direction. She benefited from their alliance. However, in the end, it was still not to be, and they sadly came to realize they both needed to go on in different directions, without each other. Realizing this did not make it any easier. Their parting was still going to be painful. The pain that was coming from their changed relationship began to merge with the pain of their knowing they
must part.
The wiser, older one sadly knows the truth of this and takes the initiative to say, in essence......"We promised to keep it light, anyway. It became more than either of us expected. Let's be grateful for what we had together. Let's part as kindly and lovingly as we came together so long ago. Let's be 'married' one more night. It will help me to let go of you, as I know I must. It will help you to let go of me, as you know you must."
For me, the song is taking the high road in the dissolution of a relationship that had become unexpectedly very meaningful for both. I 'see' him as bolstering himself in his loss and having to let go of all the good, telling himself now that everything will be fine for him, and wanting to part as lightly and beautifully as they had come together.
This is a song I've only heard within the past couple of years. I'm going strictly by my memory of the lyrics, without listening to it as I write. Leonard has remained friends with the vast majority of his lovers. He may have written this one about a past encounter, but I never took it to be that. From that perspective, however, "The Smokey Life" could easily and rightfully be construed as the social setting of a bar where they met, as the onset of their brief encounter...and where the 'maritally'-associated spending the night together for one night, which developed into a brief, conjugally-based relationship began. 'That life' can more predictably go the way that you interpreted the song than the way I have

. "One more night" of the prevailing force that joined them....and, then, a sweet goodbye.
My preference has always been to read more into the song than that, however; but, then, that's me

. Once I listen to the song, again, I may agree with you

.
~ Lizzy