In high-load, highly contaminated, and maintenance-challenging harsh environments, rotary lip seals typically rely on grease lubrication. However, there is currently no suitable model for predicting the lifespan of grease-lubricated sealing systems. This study establishes a numerical simulation model to evaluate the lifespan of rotary lip seals under grease lubrication, considering rubber aging during storage and use, as well as wear. Based on experimental results from thermal aging and standardized wear testing, the evolution of reverse pumping rate and friction torque over aging and wear durations is analyzed. A performance evolution model is developed to predict the storage and service life of grease-lubricated lip seals, enabling leakage failure warnings and providing guidance for seal replacement cycles.