This index applies to a rated average lifetime, which refers to the point in time when 50 % of the installed lamps are still burning. Lifetime is essential when choosing a light source for a special application area. It is vital to have long-lasting lamps at places that are hard to reach, which considerably reduces the risk of work accidents. Furthermore, the longer the lifetime, the less waste is produced during maintenance, which is not only reducing costs, but also having further environmental benefits as used light-sources are considered to be hazardous waste.