Guys generally don't change that much unless they're getting pitched around. It's pretty common for guys to get a little more disciplined at the plate as they mature, though.
Couple of comps for Adam Jones:
age 22-29: .321 OBA
age 30- present: .345 OBA
Reggie Smith (most similar to AJ at age 27--nice comp BTW!)
age 22-29: .360 OBA
age 30-37: .377 OBA
(different offensive environment might be a factor here)
It's not always the case though:
Andre Dawson (second best comp at 27--AJ's in awesome company on that list!)
age 22-29 .329 OBA
age 30-38 .323 OBA
He was the exact same player. Which wasn't bad.
age 22-present: .324 OBA
It's reasonable to hope that Adam can push that up to .340 over the next couple years.
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