Written constitutions, though designed to endure, are remarkably fragile, with a mean lifespan of only 17 years across all countries since 1789. This paper draws on the literature on endogenous constitutions to explore the determinants of constitutional durability among nation states. It first examines the relationship between constitutional change and regime change, analyzing the causes of constitutional demise. It then considers the role of state-level structural characteristics as well as features of constitutional design in allowing constitutions to withstand exogenous shocks. The findings suggest that certain features of constitutional design do make a difference, and can help constitutions endure: in particular, the inclusiveness of the adoption process, the flexibility of the amendment process, and the specificity of the document are crucial features promoting endurance.