For that matter, how much time do most shihan-level instructors spend on it?
As I said in the other thread: When we practice with Endo sensei we usually practice very few waza. This exactly was the reason I at first didn't like his seminars, actually. Was so different to what I knew until then.
And even when we practice a certain waza, it's not the waza itself, we focus on, but allways some detail that can be found everywhere and doesn't point in the direction of this certain waza, but is important universally. Not easy to describe. But the nameable waza are more kind of "occasion" to study something deeper, than the aim of the study.