I did some spreadsheet scenarios with different investment returns on the early money (actually the entire stream of SS income in the various scenarios out to different assumed ages of death), and different inflation assumptions.
And then as I said, the charitable deductions -- limited to the 2016-2021 period and based on my AGI, turned the decision for me.
And yes, I'm well aware that it's a percent difference for each year of delay, not a flat dollar difference. And that everything goes up with inflation on a percentage basis, not a flat dollar basis. I'm an engineer, so I'm not challenged by concepts like percentages. As a planning engineer in an electric utility, I was constantly analyzing economic decisions to pick the best plan. So this isn't my first rodeo.
And yes, I gave a lot of consideration to my life expectancy as I indicated. And yes, I'm fully aware that what matters for life expectancy is my life expectancy at the age I would be making the decision to begin taking SS, not my life expectancy at birth.
I'm not saying my decision is the right decision for everyone or even for most people.
I don't expect I'll be expressing regret in a few years, I don't know why I would.
I will in several years if I outlive my breakeven age that I figured based on my inflation and investment return and special tax situation. But I won't deeply regret it because I did a ton of reading and a ton of analysis of it. And went over it with my tax guy just to make sure I wasn't missing something obvious or making some profound error.