My wife's closest 10 or so friends are all from school era, 20+ years ago. My close friends are all people I've met as an adult - I'd consider them deep friend

My wife's closest 10 or so friends are all from school era, 20+ years ago. My close friends are all people I've met as an adult - I'd consider them deep friendships: we've travelled together, catch up regularly, know each others' parents and kids, discuss the issues of the world, etc. But, like school, you need enough time around a common place or interest to develop all that. In my cases, it was usually shared, social offices or having friends in common.