I retired at 57, and I have mixed feelings (non financial) about it. Most of your peers and maybe all your friends will be at work all day Mon-Fri. Are you ready to be alone that much, or hang out with retirees much older than you are. It’s not that I didn’t know going in, but it’s not easy to get used to. I wasn’t going to hang out regularly with 70-80 year olds, many physically limited. Some people like solitary, so people don’t.
My grandmother's cousin ran into sort of the reverse of this problem, as she got older. She started feeling lonely, because most people in her age group were either dead, of limited mobility, or simply becoming recluses, and she was still pretty energetic. She quit going to the local senior citizens' meetings, because she said it was like hanging out with her kids.
I never really thought about it when I was younger. When you're in your 20's, I guess, everybody above a certain age just seems "old" and it's easy to lump them together. But, once you get there, there's a pretty big difference between, say, a 60 year old and an 80 year old.
She's 95 now, and the last one alive, of her generation in my family. Just sold her single-family home over the summer, which had a swimming pool, and was always the go-to place for parties, cookouts, etc. Now she's in a tiny 1 bedroom apartment, and hating it with a passion.
Now that I think about it, she was about 56 or 57 when she retired. She was sort of forced out, of the federal government, when they were playing politics and favoritism in her department. Basically had the choice of retire early, or get fired. Whenever I'd talk about wanting to retire early, she'd always try to talk me out of it, and say to work as long as I can. Her main regrets, though, were that money got tight as she got older...mostly because she was constantly bailing her family members out, and letting them leech off of her.