This refers to the "half-life" of the lamp inside the projector. This is the point where the lamp is half as bright as it was when it was first being used. It will gradually lose brightness with use, and it is recommended to replace your lamp when it exceeds it's lamp life. In fact the lamp life rating is the time till the bulb is producing only half of its original brightness which has significant impact on projected image brightness.

The range of expected life ratings for projector lamps is 750 to 6,000 hours with an average of 2000 hours. Lamp life for a projector will vary based on many factors including application, installation, intake of cool air and exhaust of hot air, usage, and proper maintenance. Heat buildup can reduce lamp life and even damage your projector. Here are some tips to help your projector lamps last longer.

Many projectors have a bulb use timer which combined with knowledge of the bulbs rated life and usage conditions can be used to estimate lamp life left. The rated life is what the manufacturer estimates will be the number of hours the lamp will produce at least 80% to 90% useful brightness.

For projectors that are used under normal operating conditions (three to five hours per day in a clean, dust-free environment) the lamp will have the greatest likelihood of lasting through its entire rated lamp life.