One thing to keep in mind however is to think about your ability/desire to find work later in life after years/decades of being retired.
When you retire with a FIRE success rate of 80% or lower, you're essentially guaranteeing yourself that if you ever come across an economic calamity that was similar to the ones we've seen in the past, then you're going to have to find another source of income to supplement your savings so that you don't run dry.
Now, if you retired early in true "mustachian" fashion, your expenses should be very low, so ultimately you'd only really have to find cheap and abundant work for supplemental income. But, you'll need to find work none-the-less. Also, you'll certainly always be in a better position than typical Americans who are overloaded with debt and work 9-5 and are dependent upon their salary incomes to stay afloat on their debt. So that's good too.
However, this all comes down to a decision of whether you want to look for cheap work during times of economic stress during your retirement so that you can ensure your 75% "success rate" turns out to be 100% successful. Or, do you want to just work 2-3 extra years during your young career working years so that you have a 100% "success rate" so that you can ensure your savings amount will sustain you through even the harshest times that may lie ahead?
If you work a couple of extra years to pad your savings to a 100% "success rate", then you can think of it like self-insuring yourself against economic calamity. Sure, you might have worked a couple extra years for nothing (if there never ends up being an economic calamity), but that insurance will still provide some peace of mind for you during retirement.
For me, since I enjoy my current job, I'll gladly work a couple extra years to pad my savings while I can and ensure that I won't ever have to supplement my passive income during retirement. That doesn't mean I won't adjust my withdrawal rate according to how well the economy is doing, but merely ensuring that I won't ever need to go back to work again. That's why I'm willing to work a couple of extra years to achieve a "100% success rate".