The path to ER progressed in such extreme slow motion that it didn’t even really qualify as a “final decision” - more a very slow evolution. And the motivation for it changed over time. In retrospect, the thought process and decisions were at least as much on the subconscious level, as they were at the conscious analytical level.
DW and I had sometimes talked about retiring early in order to have more “golden retirement years” together (she is significantly older). But, events in life kept us too busy in other ways to really concentrate on it and make serious plans.
Then DW developed a progressive neurological condition. Early onset, and a variant which progressed very slowly, so slowly that it took a few years for us to fully realize what the issue was. Again, dealing with that change kept us too busy to fully concentrate on the notion of ER.
But, in the back of my mind, even if not at a completely conscious level, it was becoming clear that DW would need more and more help and attention as the years went on, and that it would be less feasible (and safe) for me to work full time (or maybe even at all). She had retired by that point.
So, over a period of years, I began to partially work from home (but full time)... then to work more from home... then to switch to part time... and finally, to give notice (6+ months out, out of courtesy to an employer that had been very accommodating). A lot of this was happening as much out of subconscious thought, as out of detailed plans... and there was also a psychological component. Even if you consider yourself very independent-minded, the hooks of internalized societal expectations (e.g., working as long as you can is the only dignified thing to do) can be a lot harder to disengage than you expected.
In parallel with that years-long transition, was running multiple spreadsheets... FireCalc... etc. ... nine ways to Sunday, and finding it difficult to envision a scenario in which our backs would be to the wall. In reality, we probably could both have been retired years earlier... but working longer gave us more flexibility, including in moving to a house that would make it easier to take care of DW. So, hard to say whether we worked too long, or not. Sometimes one looks back and what looks ill-considered from one angle, looks fortuitous from another; or what one thought one did for one reason, was indeed the right choice, but maybe for another reason that one was aware of on a different level.
ER is still an adjustment for us... but it seems the right path, taking everything into consideration.