PB,
That is something I considered too. I could have waited until I was 65 or even 70 (considerably more at 70) BUT truth is, I didn't want to wait. I considered the fact that IF I waited, would it still be there.
Also, the summer before I decided to put in for retirement, one of our school counselors (age 56) had just retired, moved to another state. She still had boxes yet to unpack and they found her dead slumped over her computer.

That sort of did it for me. I kept thinking, "I don't want to die at work or while I'm working."
It's an individual choice for everyone. If it is one's only source of income then it probably might be best to wait til you're older but it all depends on how you want to live your retirement.
TIS