The installation and operation of an ELT and the associated astronomical instruments requires considering the reliability aspects (the ability to work satisfactorily for a specified time under given environmental conditions) and the maintenance/maintainability aspects from the beginning of an ELT/instrument project. In particular, for equipment working in the extreme antarctic environment the reliability and maintainability characteristics are the main factors influencing, i)the availability of the equipment for the scientific research activities, and ii) the annual and the long term operation costs (Life Cycle Costs, LCC). These characteristics have to be designed and built into the equipment. The presentation describes the general strategy to be followed, the main activities to be done, and the decisions to be taken during the individual project phases from the identification of the user needs to the installation, commissioning and operation in order to guarantee high equipment availability and optimized maintenance effort and costs.