often wrote:
the easiest analogue i can give is like knowing your friend's dad as "Mr. Jones" since birth. You can't easily call them "John" later on after having that concept of "Mr. Jones"
For all my teachers before university, I've always addressed them with the prefixes Mr., Ms., etc. Even 20 years after school, when some of them told me it's no longer necessary, I still do it, and will likely continue forever.

With other teachers (in the US), after college, I always address them by their first names.

Like Go, there are always exceptions. There is one teacher, since 1987, he'll
always be my
Sensei.
(
Local time Mon Dec 29, 2014. 08:56 am )