The so called 4% SWR should be adjusted down now, because a lot of rates are down, and of course a smaller withdrawal rate ensures your money last longer, hopefully until you are gone. At least until then.

The original study also uses 30 years. I'd think that for those who are risk averse, the safest is to plan for as long as realistically possible, but then again many things can happen in 30 years and most people are flexible enough to prepare for it.

The safe thing to try to do is lower withdrawal rate, increase your FI target more than the 4% / 25x rule (meaning, save or invest more), and target longer.

If you can somehow get more than 30x to 40x your annual expenses, withdraw less than 3% or even 2% per year, then you are more likely to have your retirement money last longer than 50 to 60 years. If you don't live long enough to spend it all, your heirs will have something.