As dams age, operating costs increase and associated risks intensify. Addressing the mechanisms influencing dam economic life is crucial for accurate assessment and operation management. Dam economic life is affected by social and ecological environmental factors, whose types, relationships, and influence degree vary over time. In this study, influencing factors were identified across five dimensions: safety, cost, benefit, social impact, and ecological and environmental impact. Using the Random Forest method, the interaction degrees among individual factors were analyzed. Using on Markov theory, the Decision-making Trial and Evaluation Laboratory (DEMATEL) method, and the Interpretative Structural Modeling Method (ISM), a time-varying analysis model was constructed to reveal the mechanisms of these influencing factors. The model was applied to the Luhun Reservoir in Luoyang City, Henan Province, China. Results showed that during the first 20 years of dam operation, factors such as total reservoir capacity and management level considerably affected dam economic life. Over the next 20 years, total reservoir capacity and population protection became the dominant factors. Dam economic life can be extended using management measures, including improving storage capacity utilization, enhancing silt control, and increasing flood control storage capacity.