When Kenshiro Abbe Sensei introduced Aikido to Britain in 1955 it was his teaching that once a student reached Shodan he/ she would be referred to as Sensei - I consider if that was the wish of my teacher, then I have no wish to change his teachings - This method still continues in the `Ellis Schools of Traditional Aikido` after 55 years - I am sure that it will continue as such once I am gone.
Co-author `Positive Aikido`
That is quite exceptional. Did he ever give a reason for doing this? Is it because he had a need for instructors on a rather short term in order to spread Aikido?
As a contrast, I remember that Ken Cottier (7th dan Aikikai Hombu shihan) never liked to be addressed with sensei - not in the dojo and certainly not outside the dojo.