To be clear, none of my 'rant' was directed at you or anyone. Just a rant. I wanted to clarify this as I used you're quote as a spring board
As for the post above that I've quoted, I understand what you're saying as far as a teacher's recert. And I can understand this as I have to have recert/continuing education/logged teaching hours for some of my LEO instructor certs. And I support this as new material may be added to the outline to be passed on to the student. Or material may have been taken away if found to be ineffectual or something better has replaced it. I have annual recert training on everything from firearms to CPR to defensive tactics. This is as a Deputy, but more often than not I'm teaching the class which satisfies both in-service as well as instructor recert in one shot. So I can see recert for teachers. I can't see it for students though. If new material has been added to the art, or a different yet better way to do something then simply add it in or make it a criteria for a new Dan level. This in and of itself supplies a motivational goal for the student.
I could see something like: white to black belt is the b/p/k stuff. First Dan to second Dan is the beginning of locks. Second to third Dan introduces throws and sweeps. Third to fourth Dan gets into weapons etc. This is just an example, but just as yellow to green (or whatever) introduces new concepts to train in (and/or master) the Dan ranks could do the same thing. Thus keeping the attention of the student and supplying a boat load of motivational goals.
If some instructors don't have additional material beyond the first Dan (or whatever level) then that is motivation for the instructor to him/herself gain additional knowledge. Yes, it takes time and effort. But it is part of being the very best instructor you can be and offering the most you can possibly offer to the student.
Some of my continuing education in the arts has been 'are you frigging kidding me this hurts' painful. But it was time and energy well spent and I learned material that I can now pass on to students.
I just think there are better ways to motivate a student while at the same time providing a service worthy of what is being charged for the venue.
I'll second Daniels suggestions as well as being excellent motivational tools that enhance interest while keeping the doors open and food on the table.