The Novice network automatically fills mentor spaces up to a 100. Every time a space opens up it adds a new mentor.
I think it is perfectly fine this way. We don't need an excessive amount of mentors teaching a small amount of sprouts. We need mentors to be there when sprouts ask their questions. That might mean it can take a while before you get your chance at actively teaching, and that is fine.
I can understand the excitement of becoming a mentor and wanting to teach, but being a mentor is not about teaching no matter what. It is about teaching someone that needs help, when they need help.