<p>Circular economy debates often acknowledge material lifespans and delays, but time is usually treated as a contextual issue rather than a structural barrier. The contribution is to reframe circular economy transitions as intertemporal processes by treating time as an endogenous structural barrier. A framework is developed that classifies goods into short-, medium-, and long-lived categories, demonstrating how lagged inflows and valuation biases suppress aggregate circularity even when technology improves. By making temporal mechanisms explicit, the analysis explains why indicators remain stagnant despite policy and efficiency gains. The contribution is to introduce time as an endogenous barrier, integrating insights from environmental and resource economics into circular economy theory and showing how delayed substitution shapes both firm investment and policy outcomes.</p>