We study dynamic contests in which players vie for a prize through a sequence of battles. We examine how contest rules—mappings from outcome histories to the winner—shape dynamic incentives and govern rent dissipation. A strong discouragement effect arises in common formats such as tug-of-war and best-of-K, preventing full rent dissipation. We trace this effect to a structural property of these rules, exchangeability, and leverage this insight to establish a sufficient condition for containing discouragement and achieving near-full rent dissipation. An application illustrates how uncertainty about the dynamic competitive environment can similarly lead to almost full rent dissipation.