The number of work years needed before you can retire can entirely be determined by the % of your take-home pay you save. For example, to retire in 35 years (assuming a 0 net-worth), you need to save 21.5% of your money. If you're on HackerNews, you probably have a high enough salary where that's absolutely doable. Bump it up to 35%, and you can knock another decade off of your working career.
This page, like all FIRE stuff, is making rather positive assumptions about the ROI on savings (they’re assuming 5% over inflation). I, for my calculations, am personally assuming 0% growth - I just don’t want to end on a street when I’m 65 or 75.
You can play around with the numbers here: https://networthify.com/calculator/earlyretirement