I would add a third parameter.I do not know what normal or legal means.
I know people who have retired at 52. Others still working in their 70's. DB's are few and far between now however many existing one focus maximum benefits on years of service or a combination. not age. My DB was based on retirement at age 62. CPP can pay out from ages 60 to 70. OAS from 65-70.
For many there are only two parameters. When they can afford to retire and when they actually retire.
Forced to retire due to poor health or unemployment. Sadly, some don't get to choose when they retire. Not sure if this was included in your second parameter of when they actually retire.