Yahoo! Finance: The first wave of Baby Boomers turned 65 earlier this year. Once, that was the official retirement age, the birthday after which you could spend entire Tuesdays on the golf course with no judgment. It was also the age at which people would start to look askance at the office.

Indeed, a broad swath of older workers once faced mandatory retirement age policies, and until this spring, Great Britain had a “Default Retirement Age” (DRA) of 65. Past that, an employer could dismiss an employee simply because she was getting on in years.

But Britain’s DRA has now been largely phased out, and social norms are changing. According to the Bureau of Labor Statistics, in the U.S., the labor force participation rate among people aged 65 to 74 rose from 16.1% in 1988 to 25.1% in 2008. To be sure, the increased participation among older workers is at least partly due to financial necessity — though the increase began during good times, rather than simply spiking during the recent recession. But even if you are financially comfortable, or if you can be flexible with living expenses, this increase in working seniors raises different questions: in the absence of social norms or laws, when is the right time to retire? What are the signs that you should stay, and what are the signs it’s time to move on?