KoKo Ed makes a good point. This will continue to be a hot-button topic simply because the make-up of each team changes from year to year. Kids leave the team, younger team members mature (the difference between 9th graders and seniors is astonishing), new members join, mentors gain experience and change as well.
Since the make-up and personalities of the team will change year-by-year, the role of team mentors will continue to evolve. Know how "much" to mentor is just one of many challenges that face team mentors every season.
Fortunately, most of us mentor for the big bucks!
Peace