A few years ago I began maxing out an HSA as a savings vehicle, but also used it to cover our out of pocket costs.
Yesterday while confirming that my employer's annual lump sum contribution had been made to the HSA, I realized that the invested balance threw off far more money than we spent on our out of pocket costs last year, and in a normal year returns would even cover the max out of pocket under our insurance plans.
For as long as we retain our current employer-sponsored insurance, the investment increase in a pretty piddly little HSA will take care of our out of pocket costs. That's pretty cool.
For anyone looking for savings motivation, you could disaggregate FI into categories that would be pretty rapidly attainable: housing FI, food FI, healthcare FI, education FI, etcetera. To me, it feels more concrete than thinking I'm 54% FI.