Initially, under the Flight Test Program, Mir was scheduled to operate up to 5 years. The station operated nearly 3 times as long (its service life reached more than 15 years).
Under the Flight Test Program, the Modules were scheduled to fly as part of Mir for a period of 3 years (1095 days). Below are given the actual operating periods of the Modules as part of the Orbital Complex (as of December 31, 2000).

Most of the onboard systems have significantly exceeded service life characteristics specified in the log books for assemblies, instruments, units and systems as a whole. There were instruments, which operated more than 10 times longer than originally specified service life.
In order to ensure a prolonged operational use of the Mir OC, a special procedure was adopted envisaging extension of its operating period on an annual basis with generation of the required special reports on the systems, as well as final conclusion of General Designer. In so doing, it was allowed to operate the systems with exhausted service life and use them until failure occurs ensuring the required reliability and safety level.