He aged a lot as governor. That was a high stress job. most dudes in their late 50s, worth that much $, would have spent their days in the spa, on vacation, staying in shape. He had a very very stressful job that he wasn't even doing for the money.
I think he'd look 10 years younger today had he just stuck with 1-2 quick movies a year and enjoying life the rest of the time.