That is why https://www.firecalc.com/ exists. The idea is that you save enough that over all the possible starting years, you would end up with money instead of broke, for the length of time you think you'll be alive.
Another similar and popular US-data-only tool that is fun to play with is cFIREsim: https://www.cfiresim.com/
(Edit: of course, US companies have non-US revenues - helps out a bit)