Ok, almost a year after I decided to try this, I have stripped my laptop LCD, removed the anti-glare, I have the board for it. I have tested my equipment (including the 450 watt metal halide transformer my dad had laying around.....yay for helping him clean the garage eh?)

So, EVERYTHING works. I built a sample box, it worked (it remained merely a sample because I didn't bother to make room for the controller board...).

I have decided I want to run fans and I want to filter all my air flow to keep dust out (my place is incredibly dusty).

Only problem is, I fall asleep easily (narcolepsy FTL) and I don't want to start a fire if the filters clog. So I have decided to use a latching temperature sensor relay. (according to dad it is called that...he is the electrical guy, not me).

That's fancy talk for: Something that turns everything off if it gets too hot (except a LED to let me know to change the filters), and won't turn back on just because it cools down (save the lamp), even in the on position, until the power is cycled off then back on. (Took me forever to figure out how to word that so he would know what I wanted).

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So my question is, what is the lowest temperature one should allow any part of their rig to get? I am using MDF to build the box, it can handle over 400 degrees F. I am assuming the lenses/LCD will fail long before that.
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Odd way to phrase the question but in general we use the LCD as the critical portion of the build thermally speaking and we attempt to keep it at somewhere in the vicinity of 90 to 95 degrees Fahrenheit maximum give or take a few degrees depending on the size of your cojones.

My build exhausts from the lightbox way, way hotter than that but I can keep the air going over my LCD a few degrees above ambient.

During your testing phase if you see any part of your LCD going dark SHUT DOWN AND COOL IMMEDIATELY AND REMEDY THE OVERHEATING PROBLEM.

Yeah, I wrote that while fighting to stay awake... In retrospect, I meant the maximum operating temperature of the component(s) most sensitive to heat.

You don't say where you live, but if you live in the US, you might want to incorporate an attic fan thermostat (Google search of LL forum) into your enclosure. You can wire it so that it shuts off your lamp, should the inside of your enclosure get too hot.

If you're not sure how to do this, there are plenty of wiring diagrams (Google) showing where to place it.

I realize I am pulling this out of obscurity, but 90-95 degrees F? That's below normal body temperature, right? The air coming out of the monitor I am using right now is higher then that... I don't mean to seem ungrateful, but I have finished the schematic and am purchasing the components. It would be highly annoying to purchase parts that will trip prematurely. Also, what is an acceptable temperature for the inside of the light box (or rather, what is the "overheat" temperature)?

During the testing phase I have to run the projector with the vents covered till it trips. I then have to run it for 24 hours straight. I assume I can hurry the "going dark" test along by running it as black screen, right?