This assumes the Instructor "Thinks" he's perfect and does not continue to evolve his own practice and pass this on to his students...
In some ways this is even worse. In a non sparring art I've seen several instructers look to "evolve" the practice. Trouble is without resistant sparring, the evolution is based on theory. So it both takes you further away from the source (which let's assume was once effective) while at the same time not having the redeeming feature of being an improvement based on combat experience. So it becomes a lottery whether such "improvements" are actually martial improvements.
[Rex] Bow to your sensei! [/Rex]