Electrification of public transport is inspired by the increasing concern about greenhouse gas emissions. Studies in this realm were conducted to smooth the sustainable transport mode transition, whereas very little attention has been dedicated to modeling the effect of battery degradation process on fleet operation. To fill the research gap, a long-term electric fleet management framework is developed, with fully considering the practical battery capacity loss within charge and discharge cycling. As the battery aging rate is highly dependent on the state of battery charge, we propose to constrain state of battery charge within a predefined range and quantify its cost-effective feature through lifecycle cost analysis. We employ 6 groups of the selected ranges to valid the model and conduct a cost-benefit analysis through comparing their corresponding lifecycle costs. It shows that the battery lifespan can be extended by up to 3 years and the lifecycle cost of electric bus fleet can reduce 24.7% through keeping the state of battery charge within a low and narrow range. A number of managerial insights stemmed from the numerical cases were fully analyzed. The framework and results of this study were expected to serve as a reference for transit operators to make sustainable management strategy for the next generation of public transport.