Originally Posted by robbyc30
I don't know who came up with it, or when it was, but I definitely remember reading about someone from one of the pj companies (maybe Infocus?)saying that cycling the bulb takes about 2 hours of life off it. Several of the more experienced members seemed to accept that as a general rule. So if you'll be gone 2 hours or less, leave it on;more than 2 hours, turn it off. Since then, I have used this guideline with my own pj. YMMV.
I was told once by a projector lamp manufacturer that each strike cycle on a projector lamp erodes the electrodes by about the same amount as a hour of typical lamp use. I do not know how accurate that number is, but it probably varies a bit with different lamp types or ballast designs. However, remember that there is more to consider than just lamp life.
1. Not all lamp strikes are the same. Striking a lamp can cause much more electrode damage if done while the lamp is still hot. In the extreme case imediately re-striking a lamp when it is still very hot has been known to kill the lamp. When you turn your projector off make sure you let it cool for several minutes before re-starting. Most projectors should have something in the insructions about acceptable cool down periods.
2. While you do not want to cycle a projector lite on and off like you might a bathroom light fixture, try to keep this in prespective. If you get average life out of your lamp the cost is not much more than about 15 cents an hour. If you are taking a break longer than say 20 minutes , why not turn the projector off? The difference in lamp life for much longer than this is getting close to a wash. Do you really want to leave the color wheel spinning at full speed for that whole time? Do you want the light dump, lcd panels, DMD chip, homogenizer, etc taking all that extra heat? And what about the wasted electricity?
The lamp may be the only stated consumable in the projector, but many parts in these projectors are know to have limited lifetimes. For me, I try to plan my use of the projector so I do not end up turning it on and off like I might a TV. But I also do not worry if I occationally do need to turn it off for those longer breaks. For me that means I do not generally leave it on for longer that about a 15 or 20 minute break. YMMV