Enhancing the reliability of Electronic Components and Systems is optimizing certain (usually undetermined) characteristics of a system in a certain (usually undetermined) phase of the life cycle. ECSEL JU European Project “Intelligent Reliability 4.0” rephrases this objective to enhance and ensure reliability of ECS by reducing their failure rates along the entire value chain. But does this also encompass the maintenance style and activities? Inspection, fault detection, diagnostics and prognostics at component and subsystem levels will contribute to quantitative assessment of performance and other properties of system and application level functions that can be linked to a multidimensional impact-space specific for the organisational context. The public-private context-driven weights of this impact-space, or Health Indices determine to a larger extend which maintenance style is most effective and affordable. The examples illustrate the role of fault detection, diagnostics and subsequent prognostics in relation to the maintenance strategies and the intended contribution to the corporate values. Attention is paid to the bottom part of the bathtub curve: “the range that covers most of the operational life, where maintenance style, repair and system configuration largely determine the system performance”. Operational life can be extended by repair or replacement of components in order to reset the wear-out process and keep the system failure rate and availability at acceptable levels. The maintenance style will be affected by the possibilities and limitations of diagnostics to monitor the wear-out condition of a component or the ability to classify a component to early wear-out- or normal components. But also the availability of work forces may determine the maintenance style. The optimization of the mix of maintenance styles is subject of Reliability Centered Maintenance.