For your info, I have been instructing for ten years and have 4000 hours instructing. I am actually an FIC instructor , because to me the job of teaching is a very responsible and important one, far more responsible than being a coach driver in a big jet. If I teach one guy to be an instructor, I am influencing a whole generation of pilots.
I used to work in the City and could have earned megabucks, but to me the joy in seeing a guy getting his first paid flying job is so much more reward. I also still enjoy the thrill of the first solo. As GA pilots we are very very privileged. We enjoy the most amazing views and escape the mundane. My life was changed by learning to fly and I believe that I can change other people's lives. That is what being an instructor is about. If you get cynical and stop enjoying the job, then do something else and leave the instructing job to someone with enthusiasm. I have not lost my enthusiasm after ten years, if anything it is greater.....