In working though my thoughts on the subject I reviewed the careers and aging patterns of 14 top-flight offensive catchers. Nine of them are in the Hall of Fame; the five who aren't either are not eligible or are (my opinion) a mistake by the voters. There were three guys I considered including but didn't; I chose a deliberately high standard.
The 14, in alphabetical order: Johnny Bench, Yogi Berra, Roy Campanella, Gary Carter, Mickey Cochrane, Bill Dickey, Bill Freehan, Carlton Fisk, Gabby Hartnett, Ernie Lombardi, Mike Piazza, Jorge Posada, Ivan Rodriguez and Ted Simmons.
Left out: Joe Torre (spent much of his career at first or third base); Thurman Munson (died at age 32) and Elston Howard (caught behind Berra in the Yankees system, he didn't become a regular catcher until already into his 30s).
Everybody's career is a bit different, of course. None is a perfect comp for Mauer, who, as I've written before, appears to be a historically unique player.
What I'm going to do here, bit by bit, is detail the aging of each of the 14 — something there simply isn't room to do in the paper. Hey, I've done the work, I might as well share it with you.