Abstract Many one shot devices are kept in storage and taken into use when required. This paper examines the deterioration of the devices when in storage. For a complex device limited non-destructive testing and repair is possible short of using it in a destructive test. The tests are not perfect and can give false positive and false negative results. When a fault is indicated a minimal repair is carried out. The objective is to establish levels of reliability of individual components which together with the inspection regime give a particular level of reliability in the delivered components. Assuming a general distribution for the time to fail in storage the likelihood is developed and used to estimate the parameters of the model. The estimated model can then be used to explore different inspection and repair policies.