But you won't because the reason why you spent time together was someone paid you to. How many people are you still hanging out with the company you worked 10 or 5 years ago? Very few if any..
For n=1: Most of my friends, and definitely my closest friends. That said I made more close, long-term friends as hire #11 at a startup than I did as hire #111 at a midsize tech company.
Depends on the person. I still text a guy that I worked with 5 years ago and we still play games together online from time to time. I don't keep in touch with my old boomer manager though because we don't have any mutual interests.