Many one-shot units are often stored for extended periods before their single use, during which they may experience on-shelf degradation and failure. To ensure these units perform reliably when needed, timely inspections and maintenance are essential. However, inspecting and maintaining every stored unit in full detail can be economically prohibitive. In this study, we propose a joint sampling, inspection and maintenance (SIM) plans tailored for heterogeneous one-shot units. Rather than examining every unit, our approach involves inspecting a selected sample to assess overall performance, followed by an imperfect maintenance process. The optimal SIM plan seeks to balance the availability of reliable one-shot units with the efficient use of SIM resources under various scenarios. This is achieved by determining (i) the criteria for selecting inspection samples and (ii) the appropriate maintenance and restoration thresholds for the products. A numerical example based on a type of airbag is provided to demonstrate the effectiveness of the proposed SIM plans, along with recommendations for the SIM scenarios best suited to different circumstances.