I have three mentees and I have two very good mentors of my own.
As a mentor: Here on this community actually! And the other two were in person in a former workplace
As a mentee: One was assigned to me - I had a choice in who it would be and I kept the one that was chosen for me because she's amazing! The other I asked via email but only because I was interstate at the time. I would have asked in person because he sits two desks over from me.
As a mentor: It's a bit random. They kind of reach out when they need me and we make it work. Sometimes it's casual and sometimes it's organised- it depends on what's going on and where everyone is located. One of them is overseas!
As a mentee: Both have scheduled catch-ups with actual goal setting going on but I'm also in contact with them every day so we chat all the time. I don't have to wait for a scheduled catch up to ask them mentor- y questions.
As a mentor: It varies. It depends on what's going on and what they need from me. It's flexible and we meet each other halfway.
As a mentee: our scheduled catch ups last for 1 hour and happen roughly once a month. If we can't make it, we reschedule. We never cancel. Random chats tend to be quite quick and it's just about being considerate of each other. It's a relationship like any other- it's flexible and it's all about give and take