What withdrawal rate can I use if I only need my money to last 20 or 25 years?

Shorter horizons allow higher safe withdrawal rates because your portfolio has fewer years to encounter a ruinous market stretch. Bengen's and the Trinity Study's work implies that over a 20-year horizon, starting rates in the range of 5% to 6% have historically held up, versus about 4% for 30 years and closer to 3.25% to 3.5% for 40 to 50 years.

This matters for people who FIRE later, say in their late 50s, or who plan to bridge only until Social Security and a pension kick in. If you just need income for a decade or two before other guaranteed sources start, you can spend a larger slice each year. Match the rate to the actual length of the gap you are funding rather than defaulting to 4% for every situation.