(noun): A long life, the length or duration of a service.
            Usage: Longevity has two specific meanings. The first is the length of life, but the noun specifically refers to a life that is already quite long. "She has enjoyed health and longevity" means that her life has extended farther than most in terms of length. In a second context, generally in employment, longevity refers to the length or duration of one's tenure in a certain capacity. Employee bonuses based on longevity are given in larger amounts to those who have spent the most time with the company.
           Suggested Usage: It's easy to use the word longevity incorrectly, since it appears by its nature to refer to length. "I didn't enjoy the longevity  length of that church service!" you might say as you walk into the parking lot after a two-hour sermon. Feel free to misuse it if you must, but enjoy the benefits of longevity (that is, a long and fruitful life) as you increase your lexicon to include correct words and definitions. The longevity -- er, length -- of your personal vocabulary list absolutely depends on it.
Source: YourDictionary