To maximise bulb life, what’s the minimum length of time an LCD projector should be turned off for?
Bulbs for my projector are awfully expensive (it’s used off and on for about 12 hours per day) and contain mercury, so I want to replace them as rarely as possible.

So how long does a gap between uses need to be before it’s worth turning a projector off? If I’m not using it for ten minutes? Thirty minutes? Ninety minutes? (For fluorescents, it’s supposed to be 15 minutes, but projector bulbs are super-hot, so I assume undergo much more stress when turned on/off.)

I do try to replace the bulb when the warning message appears, but sometimes bulbs fail before that and sometimes someone else is using it and ignores the message.

Converting an opaque projector to a decent slide projector?
This is the projector I have… projector

I’d like to use it to view some slides and have an approximation how they will look on a real slide projector