I have a handful of girlfriends with whom I can call after several months of not seeing/calling/emailing and be right back where we were...guys too. But this is more in response to 10:31. It just depends on the person...

Guys or girls?

I can call my college buddies that I haven't talked in years and be right back where we were.

Girls, they start w "why haven't you called" inquisition and gotta listen to their litany of whines and sob stories and kids stories, etc.. And that's just on the first call!

I have a lot of low-maintenance friends. They're still my friends, not just acquaintances - we do seek out each other's company (in-person, phone, email,etc) when we can. But a lot of them have moved out of the area and we're not necessarily running in the same circles anymore.

Acquaintances are people who I see (or used to see) frequently in the community but don't make any attempt to get beyond small talk or hang out together.

I have friends I talk to maybe once every 3 years. But, if we happened to ever live in the same city or visit the same city, we would be BFFs almost instantly. There are also people I know (moms of kids' friends) whom I consider acquaintances, but not someone I'd normally hang out with.

OP, your description is of a low-maintenance friend.

Labels are tricky. PP hit it spot on with what I would call a "true" acquaintance. I have never thought to divide what I consider acquaintances into "true" acquaintances vs. budding friendships/low maintenance friends. There are quite a few acquaintances that I would qualify as low maintenance friends, now that I think about it.

I wouldn't worry too much about labeling enjoying one another's company and catching up when there is time.

Friends. Acquaintances, you have their work number at most.

I never call acquaintances. For me acquaintances are mothers I know but don't hang out with unless there is something we are doing in common.

Where is the line between the two?

If you speak to your friends every few months and see them once or twice a year which category is that? I don't have the type of friendships where we are constantly in touch but we do speak every few months or so to catch up. Someone may be pregnant or has a new job, moved, etc...