An estimation of MTTF (Mean Time To Failure) is used to determine how long a non-repairable Item may function before failure, ie a Component that cannot be repaired, only replaced).

It can only be statistically estimated, and may not be relevant in every instance the component is used.

Many factors influence a components failure including stresses upon the component in use, and external factors including temperature, vibration etc.

For an associated function, see MTBF (Mean Time To Failure) for assemblies.