Key Takeaways The 4% rule started as a research-based guideline for a 30-year retirement, not a promise that your money will last no matter what.​ Longer retirements, lower expected returns, and rising health care costs make a one-size-fits-all 4% rule less reliable today.​ Flexible strategies—like dynamic withdrawals and guardrails—help you spend more confidently while adjusting when markets or your life change.​ If you’re planning for retirement, you’ve probably heard the “safe” 4% rule: withdr ...