I had a pediatrician until I was 18 or 19. I remember that my mother came with me I went to him for a final check-up close to my 18 or 19 years old birthday (along with my 1-2 years old niece lol) as he would not take me anymore afterward. It was a bit odd, especially because it had been a couple of years since I had last been to him, but I enjoyed seeing that his office stayed the very same (very sterile, yet stuffed with of cute teddybears and toys) ever since I remember it.

However, whenever I had a medical emergency, I'd just go to one of the best hospitals around (the one I was born at), not to him. After a certain age, I would go to him mostly for regular check-ups.