No statistician retires with a 4% SWR for a retirement duration for more than 30 years without the assumption they will have to go back to work or slash spending.
So, if we accept this statement, what perhaps might be more helpful is to suggest what actual steps a statistician would take if they saw things going off the rails.
If the 4% rule is too simple/bound to fail, what are the alternatives? Or at the very least, what are the real, statistically informed red flags that signal corrective action is needed along the way? Something like:
25% drop in portfolio value => drop annual expenses 50% and/or bring in X in additional income
Also, for those based in the US, does this take SS into account? Granted not many of us have budgets that would be met by SS alone, but most will get something from the program. In my case once I start taking SS at age 70 my predicted withdrawal rate will be in the 1% range. If I started taking it at age 62 instead, my withdrawal rate would be in the 2-3% range. I FIREd at age 46 so the period I really need to be worried about is 16-24 years, not 30+
Ironically those who stay in stressful work situations long enough to get to a sub-3% SWR pre-FIRE are probably shortening their time in retirement significantly due to the damage chronic stress is doing to their health. For me the risk that I might have to have a simpler lifestyle as I get older is worth the benefit of being able to get older!
A statistician would do an analysis themselves using a 50-year retirement period as opposed to a 30-year retirement period. Find a SWR that results in under 1% failure rate, use this, with buffers such as SS or the ability to return to work. One of the most basic tenants of stats is not to extrapolate and using an estimate from a 30-year time period for a 50-year period is such a violation. Extrapolation does not indicate failure, but a violation of stats rules. Garbage in garbage out.
In my simple analysis, 1% SWR never fails in a 50-year time period, 2% fails less than 2% and a reliable SWR for FIRE. Failure rate geometrically increases with SWR. One can get to 2% by cutting spending or working part time, but 4% for a 50-year retirement is aggressive. But this is like telling people ice cream makes them fat, nobody likes bad news and many just keep eating ice cream, watch Oprah for affirmation and complain about fat shaming.
I would argue that there are many who blindly follow 4%, I've also seen some retirement "gurus" promote a higher SWR for longer retirements, which is absolutely insane and reveals a lack of understanding methods to create the 4% estimate.
If anyone thinks that filing out TPS reports or sitting through action plans meetings are stressful, think about the stress caused by running out of money or cutting it close after one can no longer work. The latter is stress, the former is just annoying and motivation for cartoon characters/comedies.