I think 2012 was about his norm. Scouts have long questioned whether he was anything more than a .240 hitter at the MLB level. He has, outside of one season, always been an aggressive swinger/low walk type of guy.
As for the peak defensive thing, it was from a subscriber article on Bill James online, but was referenced by Rob Neyer here.
One of the first things that is becoming apparent from better defensive measurements is that defensive value peaks earlier and fades MUCH younger than offensive value. Players often reach their defensive peak at ages 22-25, and many players are fading defensively by the age of 28, long before 30.