My Mom retired at 62. She had something like 41 years with the federal government, or whatever it is that you need, to max out your retirement under the old CSRS plan. I always thought it was 40 years, where you got 80%, but she said that it was actually slightly more. My stepdad was a plumbing inspector for the Washington Suburban Sanitary Commission. He took an early retirement, something like 59.5, around the same time my Mom did.
In retrospect, both of them said they regretted retiring when they did, but they're both looking through their former careers with rose tinted glasses. Mom was getting fed up with the way the Federal government was starting to turn, and her catchphrase was starting to become "Piss me off enough, and I'll retire!" As for my stepdad, he has his faults, and I can't stand him sometimes, but one thing I'll say for him...he actually is honest as the day is long. And, in his career that would prove to bite him on the butt. His superiors were taking bribes to pass shoddy plumbing on big projects, especially those megachurches and such that seem to proliferate around here. They tried to get my stepdad to pass them, but he would refuse. As a result, they piled work on him, made his life miserable, etc, so he decided to go out around the same time as my Mom.
Of course, to ask either of them about that now, they'll both say "Oh, our jobs weren't that bad". But, it's also been around 10 years. Mom went out in January of 2011, and my stepdad soon after. So, at this point they've both come to accept retirement and be happy with it, and any aspirations about going back to work are probably gone for good.
My Dad was a dental technician for the Veteran's hospital in DC, or something like that. I know he was federal government, but he was on some kind of system, other than the GS-XX that I'm more familiar with. He retired at 62, as soon as he was eligible for SS, but he did it to take care of Granddad, his father, who at that point was 94, and while healthy for his age, was starting to slip.