This isn't a direct answer to the question, but if you are coding professionally (in the USA at least) it shouldn't be necessary to work for 3 decades. If you think you will burn out, optimize your life for getting off the treadmill early.
Well, the linked calculator seems bogus (at least for me here in Germany). It assumes that the income is AFTER taxes. Let put some numbers in:
Given I am a programmer in Germany And I earn 4000€ (above avg.) before taxes [1]
That means I will have around 29000€ after taxes and other social charges [2]
Now if I only spend the bare minimum (9000€) [3], I can save 20000€ per year.
Now I am able to retire after 9.5 Years according to calculator. This seems right, as if I still want to live off 9000€, but guess what: The living costs (even if I do stay single, live in the same small flat and never do any vacation) rise with the years.
Now you could argue, that a saving rate of 68% might be too much, but even if you decrease the saving to 10000€ per year, you are working around 25.2 years which is plenty of time to burn out...
Can I ask why do living costs increase with years? I believe the general trend is people having less expenses after they retire.
The calculation in the link takes into account inflation, so that (massive) aspect of increased expenses is included in the prediction.
Edit - If indeed you are planning to increase your living expenses after retiring (bigger living quarters, more expensive travel, etc) that would certainly lengthen the amount of time of work needed to achieve financial independence.
The biggest "aha" moment for me was realizing that everyone out there busting their asses and burning out to "increase shareholder value" were making me rich.
Something like that. The link above has some more info but the key is that it only works because there are still tons of people not pursuing FIRE (Financial Independence / Retire Early) and you reap the rewards of their work while you have retired early.
I'm no financial independence role mode. Generally I do try to keep my expenses down for the big items (no car, shared housing). Easy enough to save that way.
Given I am a programmer in Germany And I earn 4000€ (above avg.) before taxes [1]
That means I will have around 29000€ after taxes and other social charges [2]
Now if I only spend the bare minimum (9000€) [3], I can save 20000€ per year.
Now I am able to retire after 9.5 Years according to calculator. This seems right, as if I still want to live off 9000€, but guess what: The living costs (even if I do stay single, live in the same small flat and never do any vacation) rise with the years.
Now you could argue, that a saving rate of 68% might be too much, but even if you decrease the saving to 10000€ per year, you are working around 25.2 years which is plenty of time to burn out...
[1]: https://www.gehaltsvergleich.com/gehalt/Programmierer-Progra...
[2]: https://imgur.com/a/IArku
[3]: https://de.wikipedia.org/wiki/Grundfreibetrag_(Deutschland)