Carry that out over a season and you've got 400 carries and a broken running back. IIRC, every time a running back has gone over 375 carries or so, they've been crap for at least a year or two after. I don't think anyone's ever recovered from that sort of load.
An occasional game with 25-30 carries is fine but if your RB averages that, you've just ruined him. Even in his heyday, the great Earl Campbell averaged less carries than that. He averaged 24.9 carries a game for 15 games in his best year (his 3rd year) and he was never quite the same after that. Larry Johnson had that year with 416 attempts and he was done by the time he got to the post season.