Many rules of thumb assume a standard retirement age. Fidelity, for example, suggests saving 3x your salary by age 40, 6x by 50, and 8x by 60. On an $85,000 annual income, that's $255,000, $510,000, and $680,000.If your goal is to retire early, the math changes. Your savings have to last longer and cover more uncertainty, especially health care and inflation.For those considering early retirement, these figures highlight a challenge: many workers are far below what they'd likely need to stop working a decad ...