Here in the USA there is no 'must retire at' age, unless you are in certain professions, like law enforcement for example (my handyman said he had to retire at 55 because he worked in that field). May be the military/airforce have some age limits, but in general, for most professions people dont' have to retire at a certain age. One of my coworkers is 75, and he is a very good engineer (we all are engineers in my group). I remember that W.L.Gore had hired an 80 year old employee years ago. If you can do the job, you don't have to retire.
I have heard that in other countries there is a fixed retirement age. Germany-65, India-60. I don't know about others. I am curious as to what kind of retirement ages (or no fixed retirement age, like in the USA) there are world wide. It would be frustrating for a healthy, motivated individual to be forced to retire just because he/she hit a landmark age. Of course politicians are exempt in all countries, I think.