Systematic management of all phases of the lifecycle of an industrial control system, recently referred to as operational technology or OT for short, ensures that the system is up to date, compliant with regulations and in line with changing business requirements. This is especially true for critical infrastructure. In this way, operational resilience is improved, risks are minimized and a proactive approach to maintenance is encouraged, with a focus on safety, efficiency and long-term sustainability. The paper provides an overview of the motivations for systematic lifecycle management of OT systems, offers a description and illustration of lifecycle costs in the CAPEX and OPEX phases, emphasizes the changing role of corrective and preventive maintenance from a lifecycle management perspective, and budgeting for various activities, including cybersecurity and OT system upgrades.