For large populations of vehicles, it is often difficult to estimate how changes to scheduled maintenance plans will impact future operational availability, especially when component failure rates may not be known precisely or the operational environment changes. The primary objective of this contribution is to illustrate a Modeling and Simulation (M&S) approach which determines the minimum amount of maintenance necessary to keep a given threshold of operational availability. The analysis was performed using discrete-event simulation, maintenance data, and anecdotal information from technicians. The information was combined within a model containing over 15 variables including labor and process constraints. The analysis yielded a decision tool that can be utilized to assess several potential long term storage maintenance policies, focused on cost minimization while meeting readiness requirements.