There are a variety of reasons to practice group relamping in which a set of lamps is replaced at a scheduled time rather than spot relamping in which lamps are only replaced when they burn out. Most of these reasons apply to fluorescent and high-intensity discharge (HID) lamps rather than incandescents which have much shorter lifetimes.

• Group relamping requires much less labor per lamp than spot relamping. A worker might take as long as a half hour to retrieve and install a single lamp. If all the materials were on hand for a large number of lamps, a worker could move systematically from fixture to fixture and cut the required time to about 3 minutes per lamp. The process would also be less disruptive because group relamping is usually done outside working hours.
• Group relamping is easy to schedule and delegate to outside contractors who have special equipment and training.
• Group relamping provides brighter and more uniform lighting because lamps are replaced before their output has fully depreciated. Direct energy benefits result if the designer, anticipating group relamping, uses a smaller safety factor.
• Group relamping offers increased control over the replacement lamps reducing the chances of mixing incompatible lamps—such as those with different color temperatures.