For me (mid-40s) from a quick glance at the SSA site, I surprisingly wouldn’t take a hit if I started at 62. That assuming it’s a) there and b) not privately invested in some shitshow tying it up, etc., of course.
Tentatively, given there’s no difference between 62 and 68 for me, and I’m not exactly in idea health already, the real motivation for me to work past 62 is the health insurance.
I have no illusion that the ACA or the Marketplace will exist in its current form nearly two decades from now; and Medicare seems to have a hard cut at 65 rather than the age range one could claim SS at.
That three years between 62 and 65, without Medicare, the Marketplace, or employer paid insurance, would be a far larger risk than I’m willing to take, barring a full and complete disability.