This contribution is intended to observe special features presented in physical assets for defence. Particularly, the management of defence assets has to consider not only the reliability, availability, maintainability and other factors frequently used in asset management. On the contrary, such systems should also take into account their adaptation to changing operating environments as well as their capability to changes on the technological context. This study approaches to the current real situation where, due to the diversity of conflicts in our international context, the same type of defence systems must be able to provide services under different boundary conditions in different areas of the globe. At the same time, new concepts from the Industry 4.0 provide quick changes that should be considered along the life cycle of a defence asset. As a finding or consequence, these variations in operating conditions and in technology may accelerate asset degradation by modifying its reliability, its up-to-date status and, in general terms, its end-of-life estimation, depending of course on a diversity of factors. This accelerated deterioration of the asset is often known as "obsolescence" and its implications are often evaluated (when possible), in terms of costs from different natures. The originality of this contribution is the introduction of a discussion on how a proper analysis may help to reduce errors and mistakes in the decision-making process regarding the suitability or not of repairing, replacing, or modernizing the asset or system under study. In other words, the obsolescence analysis, from a reliability and technological point of view, could be used to determine the conservation or not of a specific asset fleet, in order to understand the effects of operational and technology factors variation over the functionality and life cycle cost of physical assets for defence.