Why does working a 35th year matter so much for my benefit?

Because your benefit averages your highest 35 years of indexed earnings, any year you did not work counts as a zero in that average. If you have only 30 years of earnings, five zeros are dragging your AIME — and therefore your benefit — down. Working additional years either fills those zeros or replaces a low-earning early year with a higher recent salary, both of which raise your average. This is why people who retire in their early 60s with gaps in their record sometimes find that one or two more working years meaningfully increases their check, on top of the delayed-credit gains from claiming later. The effect is strongest if you have fewer than 35 solid years. Before assuming your benefit is fixed, check your earnings history at ssa.gov and model the impact at wealthserene.com/tools/retirement-planner.