6 years of completely being out of sight / out of mind followed by ~6 years of being old friends.
Originally broke up because we were too young, I was an inexperienced AFC and she had a wild side that she hadn't matured out of.
She matured, mostly, and I learned DJ stuff and became my own person (that's the bulk of it, really.) What attraction we had before remained and deepened.
On a side note, no one quite ever matched up to her level between now and then, although a few were quite remarkable in their own right. Most dates and GFs in between couldn't keep up with her, though.
Now we're older. It's a long distance thing, mostly, and we know the other is seeing others, etc---separate lives in separate places will have their own momentum. Marriage or living together again isn't really an active issue--particularly marriage--since I don't see the compelling need for it. When you're younger you mostly never even question that marriage is what you're supposed to do. It's convenient for many reasons, and expectations can be overwhelming such that you never really question why. When you're older and the need or the expectation isn't there, then you can assess it more clearly.
Things change as you get older--there's much more complexity and nuance you can handle, you learn to deal with situations as they are--not as you think they should be (which is very limited, btw...)
Recommend pursuing it---? No. It may or may not happen, you can't plan it. You either become old lovers or you don't--and most likely you don't.
I can ditto drixsa's comments on other re-hook-ups.