Pre-print, Working paper: This paper proposes a dynamic model of duopolistic competition under behaviorbased price discrimination with the following property: in equilibrium, a firm may reward its previous customers although long term contracts are not enforceable. A firm can offer a lower price to its previous customers than to its new customers as a strategic means to hamper its rival to gather precise information on the young generation of customers for subsequent profitable behavior-based pricing. The result holds both with myopic and forward-looking, impatient enough consumers.