Service life

A product's service life is its period of use in service. It has been defined as "a product's total life in use from the point of sale to the point of discard" and distinguished from replacement life,"the period after which the initial purchaser returns to the shop for a replacement." Determining a product´s expected service life as part of business policy involves using tools and calculations from maintainability and reliability analysis. Service life represents a commitment made by the item's manufacturer and is usually specified as a median. It is the time that any manufactured item can be expected to be 'serviceable' or supported by its manufacturer.

Service life is not to be confused with shelf life, which deals with storage time, or with technical life, which is the maximumn period during which it can physically function. It also differs from predicted life, or MTTF/MTBF (Mean Time to Failure/Mean Time Between Failures)/MFOP (maintenance-free operating period). Predicted life is useful such that a manufacturer may estimate, by hypothetical modeling and calculation, a general rule for which it will honor warranty claims, or planning for mission fulfillment. The difference between service life and predicted life is most clear when considering mission time and reliability in comparison to MTBF and service life. For example: A missile system can have a mission time of less than one minute, a service life of 20 years, active MTBF of 20 minutes, dormant MTBF of 50 years and a reliability of .999999.

Consumers will have different expectations about service life and longevity based upon factors such as use, cost, and quality.

Manufacturers will commit to very conservative service life, usually 2 to 5 years for most commercial and consumer products (for example computer peripherals and components). However, for large and expensive durable goods, the items are not consumable, and service lives and maintenance activity will factor large in the service life. Again, an airliner might have a mission time of 11 hours, a predicted active MTBF of 10,000 hours with maintenance (or 15,000 hours without maintenance), a reliability of .99999 and a service life of 40 years.

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