[user104658]

My "true proper" friends I've known all for 20+ years (well, there's also my wife who I've known for 17 years). One I've known basically since birth. Those are what I'd call the timeless friendships - I can see them twice in a week, or once in over a year (hello Covid) and it be like I saw them yesterday. I genuinely believe it will be the same if we meet up aged 70.

Other friends, a little time and shared interests plus, yes, being able to vaguely trust them is important. Those can be shorter friendships though, people move on etc. though tbh I don't have any old friends who I wouldn't be glad to see if I ran into them, or who (I imagine/hope) don't feel the same. Can't say I've ever properly fallen out with a friend, just lost touch.

And beyond that I like to think I'm generally friendLY and I have great and in-depth conversations with colleagues etc. and I enjoy their company, but there are few that I would consider "proper" friends.