I have written about this in various forms but what it comes down to is balance. I often felt I missed a lot while teaching and now that I spend a good deal of time on just practice I realize what I was missing was the equal measure in teaching and practice. Not the practice and teaching of students but rather the practice and teaching of myself.
I believe, good sensei, tend to spend an exorbitant amount of time dedicated to students and their progress they tend to ignore that one student that is critical to teaching other students - that one student being the sensei. Let me try to clear up the muddy waters here.
When a sensei spends that amount of time on students they miss a lot while at the same time learn a lot from those students. But where it loses is when you learn from the student but fail to spend equal measure on your own studies, practice and training you don't get the full measure of what you are learning.
I believe, now which is better late than never, is a sensei must spend equal time practicing and training on their own with a total and complete focus on their practices, training and studies. If I teach one hour I feel I need to practice and train and study at least one hour physically with another hour mentally and finally one more hour of study - minimum.
Yes, you are going to read this and say, "I don't have enough time between teaching students and taking care of family, home and work (if you don't earn enough teaching martial arts)!" Well, this is a disservice to you as a sensei and even more so as a teacher. Teachers, in general, have to spend a lot more time studying and taking classes to remain certified to teach our kids so why should a person teaching martial arts (especially for self-defense) get to ignore what they learn and present to practitioners.
This also presents issues as to knowledge of the sensei. In my thirty-seven years in martial arts I have found many things that were just plain wrong that I learned from my sensei. I also found many things I never learned from sensei that I discovered or learned elsewhere that if I remained simply teaching by ROTE my students would have missed.
In order to propagate and pass on martial arts to students I feel an obligation to make sure it is always the best and most up to date and relevant teachings possible. Sensei must take equal measure of what they know toward what they teach. Learning is a never ending effort and to neglect your own practice and training for students is depriving those students of the best you can give.
Some will say that they get plenty of practice with students because of the participation they put in but they tend to forget the mental training received from that is different from the mental training they get from a personal effort without the distractions of teaching. You can argue this point saying that one does the other but they don't. The effort and self-analysis of what you do comes from a focus and diligence on you the sensei while teaching is about the student while teaching.
Yes, you get a lot especially with teaching, training and practicing the more physical aspects but what are you missing. Many of the professionals I follow in their writings tend to still place a lot of emphasis on preparation and that means they are constantly working out things they discover in the dojo, on their own for the purpose of learning and then applying - both in application and teaching applications.
I also have witnessed other solid and experienced sensei actually stop teaching to focus on the study of martial arts because of this same belief but they too may be losing a source that balances out the study of the arts - the interactions of other professionals and students, etc.
So, if you teach, spend the equal time practicing on your own for yourself. Your students will appreciate what they get, a fresh perspective each and every time you encounter those students on the dojo floor.
So goes my personal philosophy on this subject :-)