Projector bulb?...Power down between uses or keep on continuously during the day?

I was talking to a fellow teacher yesterday about the use of the projector in the classroom and we both heard different conflicting ways to properly care for our projector bulbs. She powers down between each class and makes sure the projector fully cools down (at least 5 minutes of off time), then turns it back on. I leave mine on continuously with threats to the students to stay away from the machine so they don't bump it accidentally. Which is better for the bulb in the long run?

I am assuming you have a DLP type projector which are now common place for presentations with PC's or DVD players.

I currently own a InFocus DLP projector. I have gone thru 2 bulbs already. And each new bulb is $300.00. So it is very important to try to maximize the bulbs life.

The bulb in my projector is rated at 2,000 hours of life.

This is counted as the time the projector bulb is turned on.

It is also designed to work at a specific temperature.

The projector has an internal computer that runs on its internal software called firmware.

The projector can go into various states of operation.

Initialization mode

Projection mode

Idle mode

and shutdown mode.

During the shutdown mode the projector goes into a shutdown cycle, it knows that it has to keep the fans running so not to shock the bulb. You can notice that the lamp has gone off but you can still hear the fans working for a while longer.