The Trinity study (which is where the oft-quoted 4% rule seems to have originated) is assuming a max of about 30 years of withdrawals before the money is deplet

The Trinity study (which is where the oft-quoted 4% rule seems to have originated) is assuming a max of about 30 years of withdrawals before the money is depleted. If people are retiring early, it isn't clear what a reasonable withdrawal rate would be. >...The 4% refers to the portion of the portfolio withdrawn during the first year; it is assumed that the portion withdrawn in subsequent years will increase with the consumer price index (CPI) to keep pace with the cost of living. The withdrawals may exceed the income earned by the portfolio, and the total value of the portfolio may well shrink during periods when the stock market performs poorly. It is assumed that the portfolio needs to last thirty years. The withdrawal regime is deemed to have failed if the portfolio is exhausted in less than thirty years and to have succeeded if there are unspent assets at the end of the period. https://en.wikipedia.org/wiki/Trinity_study https://en.wikipedia.org/wiki/Trinity_study (Also the wikipedia article has a number of criticisms of the study.)