It's a bit easier I suppose when I'm talking about loosely knit online personalities but also people I first meet physically, it's just interesting how once you're past highly-fluid peer groups like high school or college an acquaintanceship can be maintained over a really long period of time (years and years) with very light 're-ups' (I feel like all my verbal skills have been fried these last couple weeks so very inarticulate but I hope I'm making sense to some degree.. it's a somewhat wistful concept so hard to grasp clearly)

Most of my friends in meat-space (outside work) are people who I speak to, at most, a few times a year. That's about perfect for me.

I know exactly what you mean! Over the last 3 months I went back home to Ireland for a big event and was talking to people I haven't seen for 5-10 years as if I'd seen them yesterday. Then a friend celebrated 25 years in business in San Sebastian (I business I've been out of for 11 years) and I met colleagues I hadn't seen in that time. It was incredible catching up with all the changes (or not)and it freaked me in a good way how easily I slipped into it.

I tend to find that more than most as I not only have lived in several countries, I've had three major changes of career.
Each time I enter one of the "past worlds" it's just like switching to a different language, or putting on a different dress. I'm surprised it's still so natural. And happy. I get where you're coming from.