In most martial systems sensei have to deal with a very high turnover rate. This has become the norm in the west and I suspect it is the same in the east as well. It varies as to why this occurs but it does exist and what I am proposing in this post is "high turnover" is beneficial to the marital arts and systems.
What, beneficial, you have got to be kidding, right? Yes, I propose that such turnover is a benefit and since it is here to stay why not take a look at those benefits and then embrace them as a natural part of training, practice and application.
First, let this be a natural model that allows sensei and senpai to return to the basics and fundamentals of the system they practice. After all these basics/fundamentals are the very essence of the systems we practice. Both as an introduction to the newest participants of this form of budo and also a segway into the fundamentals that newbies often perceive as the same as basics until introduced to how the fundamentals work.
Sensei and senpai, both, are naturally sent back to the basics and fundamentals of the system with each new arrival into the dojo. It is important that both not pass this effort down to the lowest and most inexperienced kohai but rather take the time and effort to provide their guidance in this introduction. It also sets a mind-set with newbies that sensei and senpai really care about them and their efforts.
Look at it this way as well, would you want the fledgling cement pouring guy to create, set and pour your cement foundation to your home or would it be best to have those experienced journeymen to at least mentor and monitor the fledgling worker to set up and pour the foundation of your home - your dojo, your home, right?
Why would you then want your fledgling kohai to set the foundation for newbies to the dojo with what will be the foundation on which you will build a karate-ka?
As you and your senpai continue to teach these basics and fundamentals to the newbies you are re-introducing yourself to those basics but most important to the fundamentals of those basic techniques where you open your mind to discover all the various paths that the lead off and take you on that journey we call martial arts.
As you teach the new guys you will find new things, ideas and ways of implementation and application that always transfer to the kata and to kumite. Is not kata and kumite, if a classically driven traditional practice of karate-goshin-do, derived from what you learn, practice and apply as to basic waza in the model of a fundamental way?