How can you determine when you can FIRE? I know 25x is the general rule, but how foolproof is it?

Nothing is foolproof in this ever-changing world. Choosing a profession out of passion and having the luck to be situated into a favorable work climate ambience makes FIRE useless.

It really depends on the investment portfolio you are holding I guess. 4% withdrawal rate can be extremely risky, just imagine you FIRE this year and you are experiencing huge losses in your investments. 30% paper loss in the market and you still have to liquidate 4%. This will also be an issue when you FIRE earlier, because there is a longer withdrawal period.

I would want to work on passion projects that can help me be employed easily if I choose to. These could be something like content marketing, digital marketing, which has a broad application that can be applied on whatever you are interested in. In that sense while I have "FIRE"ed, I wouldnt let my human capital suffer "losses".​​​