Why is the lamp is not as bright (or dimmed) after using for a period of time?

Light bulbs (lamps) are a consumable item and naturally dim as they age. Sometimes resetting the lamp and projector can help with brightness. Unplug the projector for 15 minutes, remove lamp cover and lamp for 3 minutes, and then reinstall and plug everything back in. Using the ECO modes will also help extend brightness and lamp life.