Traditionally Speaking
There is an image today of koryū as small isolated groups of a few students, headed by one headmaster, engaged in a many decades-long pursuit of martial perfection. Something like this can be true today—many people remain students of a teacher for almost a lifetime. I know of individuals who have trained for fifty years without ever receiving certification of full knowledge of the school or a teaching license. But I do not think that this is true to the original nature of koryū bujutsu. Of course, in the aforementioned case, the students in question may simply be incompetent or not suitable, in their instructor’s eyes, but it may also be due to something else—a fundamental change in the nature of martial ryūha within Japan.