Contrary to popular belief, high rank or school ownership does not always make a good instructor. However, no matter how long you have been in martial arts, no matter your rank, being a full-time instructor in your own business will certainly help make you a better instructor. When your livelihood depends upon what you say and do and how well your students like you and learn from you, you tend to become an excellent teacher, else you go out of business. When you do not own you own school, as when you are an instructor in someone elses school, you have nothing to loose, except being told you may no longer teach in the school.
While education, training, and experience in teaching, business, management, etc. is certainly helpful for a martial arts instructor, they are no substitute for being a school owner.
Successful school owners know more about teaching a martial art and the business of martial arts than any other martial arts person, no matter their rank.