I think there are some people who are good and will be no matter how long they stay. Always good communicators, always good decision-makers, and always with the gift of recognizing + hiring good people. The qualities that work first year continue to pay off forever. That may be Maddon.
But sometimes, there can be value in change-for-change sake. A new voice, I think you tend to wake up and pay attention? Even if the new voice is essentially saying the same thing but in a somewhat different way? Second, sometimes a new voice does have something different to say, some different insights. Maybe guys have learned everything the first guy has to teach; but a new guy might offer something new?
That said, *if* you do bring in a new voice, comparison is inevitable. If the new voice is dumber than the old voice, guys will notice. If the new voice is more boring, guys will notice.
I appreciate change-for-change sake, to keep things fresh, and to bring in different insights and perspective. But if you do make a change, it's pretty bad news to bring in somebody who's worse. Huge opportunity to have players and media compare unfavorably.