Maintenance-free operating period

Maintenance-free operating period (MFOP) is an alternative measure of performance to the mean time between failures (MTBF), defined as the time period during which a device will be able to perform each of its intended functions, requiring only a minimal degree of maintenance. It was originally proposed in 1996 by the United Kingdom's Ministry of Defence, with intended application to military aircraft.

Source: Wikipedia — Maintenance-free operating period (CC BY-SA 4.0)