I have one planted in my backyard that I started from a seed when I lived in my old house. Kept it in a pot until I moved into my current home. When I planted it about 6 years ago it was in a 24 nch pot and when planted it was about 4 feet tall.
Now it's about 15 feet tall and has produced fruit for only the second time since I planted it. First was last year btw. It is about 12 years old
My tree is from a Florida avocado, not a California Avocado and there are no other trees near mine, but it still produced fruit.
It is fun to take care of them and watch them grow. Kinda like kids, but easier!!!!!