How long does it take the average person to become a senior software developer?

Gee, I dunno. I have been doing software-related work since my twenties. I have never known a senior software developer who was “the average person”.

Maybe it takes “the average person” forever and they all give up. Maybe “the average person” undergoes change as he develops himself / herself into a “senior software developer”, so that by the time I meet them, they are no longer “the average person”.

OR… maybe something else is going on. In any case, that is my experience of it.