Our societies are witnessing a steady increase in longevity. This demographic evolution is accompanied by some convergence across countries, whereas substantial longevity inequalities persist within nations. The goal of this article is to survey some crucial implications of changing longevity on the design of optimal public policy. For that purpose, we first focus on some difficulties raised by risky and varying lifetime for the representation of individual and social preferences. Then, we explore some central implications of changing longevity for optimal policy making, regarding prevention against premature death, pension policies, and long-term care.