The accelerated pace of technological advancement and geopolitical changes has intensified the risk of obsolescence in long-lifecycle systems, particularly within industries such as aerospace, defense, healthcare, and industrial manufacturing. Despite engineers’ awareness of these risks, proactive obsolescence management is often hindered by difficulties in translating technical concerns into business-relevant metrics such as cost and system availability. Consequently, organizations tend to adopt reactive strategies, resulting in elevated sustainment costs and operational disruptions. This article addresses the need for a structured, anticipatory approach by proposing a comprehensive methodology to evaluate the criticality of component obsolescence in complex systems. This study builds on best practices, standards and real-life industrial experiences, aiming to fill a gap in both industry and in literature for a comprehensive-multi-criteria criticality study. The proposed methodology employs a multi-criteria framework to assess the impact of component obsolescence on system performance, safety, and sustainability. It aims to support decision-making by enabling organizations to prioritize mitigation strategies, such as redesign, substitution, or lifetime buys, based on objective risk assessments. The proposed framework is also put in practice by a case study.