Although we rarely think of it, reliability and maintenance are part of our everyday lives. The equipment, manufactured products, and fabricated infrastructure that contribute substantively to the quality of our lives have finite longevity. Most of us recognize this fact, but we do not always fully perceive the implications of finite system life for our efficiency and safety. Many, but not all, of us also appreciate the fact that our automobiles require regular service, but we do not generally think about the fact that roads and bridges, smoke alarms, electricity generation and transmission devices, and many other machines and facilities we use also require regular maintenance.