25 years is a long time to be doing this... advice from anyone who's willing to give it?

Where do I even begin...25 years is a long time... so let's make a long story short...
Girl meets boy, they date for about a year, guy fades from girls life... girl moves on, gets married, has kids, etc. Boy does the same.
10 years later... boy and girl, both going through divorces, see each other, hang out a few times, make out once or twice... boy fades out of girls life, again. Girl meets someone new, boy gets remarried, life goes on.
10 years later, boy and girl see each other again, and again, boy and girl are separating from partners, chemistry sparks again, and this time a few months go by of spending time together. Then suddenly, boy fades away, for a 3rd time. One night, she runs into boy at a bar, and he's with a lady friend. Boy makes it pretty obvious he wants nothing to do with girl, so she stops all contact with him, deletes him from facebook, etc and goes on her way.
Last week, 4 years later, girl sees boy in the store, makes eye contact, and keeps on moving without acknowledging boy. 6 days later, he messages her on facebook, saying it was nice seeing you in the store, but that you just kept traveling on, but that he misses talking to girl.
So, obviously I'm the "girl" but TF is this? It's been a year since he's attempted to make contact, and that was just a silly Christmas video he sent via Facebook.
I don't even know what to think at this point, so I'd like some help figuring out whatever it is he's doing, cuz I'm tired. We have history, some good, some not, but I gave him an easy out by ignoring him, so why message me? Round #4? Cuz it ain't happening. Friends? We tried that, it doesn't work for us. I'll be honest, he's a great guy aside from the fade he does, and I love being around him, but I can't do this back and forth anymore.
Thoughts... anyone?
25 years is a long time to be doing this... advice from anyone who's willing to give it?
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