Sensor nodes (SNs), as constituents of wireless sensor network (WSN), are battery-powered not rechargeable devices and have limited amount of energy available. Since the lifetime of SNs is a crucial parameter for energy-efficient WSN design, it is essential to extend their lifetimes as much as possible. Here we propose a rendezvous scheme called Rendezvous Protocol for Long-Living SN, RPLL. This scheme is based on implementation of a duty-cycling technique. For each SN within WSN a unique identification number (ID) is allocated, thanks to which a collision problem is effectively remedied. The RPLL provides an on time wake-up of SNs in a fully decentralized way and fast detection of new appended SNs. Taking into account the WSN and SN working parameters, such as beacon time, beacon period, number of active SNs, and quartz oscillator instability, by using the proposed method, a WSN designer can determine the maximal lifetime of a SN, i.e. achieve optimal energy consumption. [Projekat Ministarstva nauke Republike Srbije, br. TR-32009: Low-Power Reconfigurable Fault-Tolerant Platforms]