Hey, I read a very interesting (and very old) post on Bogleheads yesterday, and wanted to share it with you, but I can't find it anymore :(, so apologies to author but I can't link to it. However, here's the general idea.
We have 2 mustachians (let's call them M1 and M2) on their path to FIRE. They have the very same age (they can even be twins, if you like). M1 had a huge downfall, and suddenly owns $ 1 million. Cool, that's even more than he needs, so he retires, and SWR states he can spend $ 40 000 (4%) per year. $ 30 000 (3%) would be quite conservative, and $ 50 000 (5%) would be quite risky. M1 is conservative, and he didn't expect having so much money in the first place, so he goes for 3%.
Five years later, the market fell and M1's portfolio is now worth $ 700k, but that's okay, the rule states he can still spend inflation-adjusted $ 30 000 (let's say 35 000 in today's dollars) and it was a conservative choice in the first place, so let's keep on tracks. Well, it happens M2 saved agressively these last 5 years, and now owns 700k, too, which allows him to FIRE. The 4% SWR rule states he can spend $ 28 000 per year, with $21k (3%) being very conservative and $35k (5%) being quite risky. M2 loves risk (after all, he has a lot of safety margins), so he goes for 5%.
No, here's the question. M1 and M2 both have the very same life expectancy, both have the very same net worth, the very same asset allocation and both spend $35k per year. How on earth can a spending pattern be very conservative and very aggressive at the same time ???
Sounds like a riddle of the Sphinx. Enjoy.