Design Life (glossary)
The design life of a component or system is the period of time during which the item is expected by its designers to work within its specified parameters; in other words, the life expectancy of the item. It is the length of time between placement into service of a single item and that items on-set of wear-out. (wikipedia 2012)
Wikipedia contributors. "Design life," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Design_life&oldid=470916040 (accessed September 13, 2012).