check firecalc.com for historical likelihood of portfolio success, given a starting nest egg and an annual withdrawal rate. The 4% withdrawal rate mentioned above is very likely to succeed for an indefinite period, and 3% is essentially impossible. This is all assuming 85% US equities and 15% bonds, and that the future looks vaguely like the past 150 years.

Despite all the skepticism above, the 4% claims are true. Not 100% chance of indefinite success, but close enough to be actionable. You can also google the "trinity study" for more info.