Get your color balance where you want it to be, with each tube giving a nice delineation of contrast range. Then, run your contrast up until the tubes start to 'bloom' ( defocussing, fuzzy image, etc) right at the point where they start to bloom...then back down 10 notches from that point. On my PJ, the way it has been set up.. this occurs at a setting of 50 (contrast scale of 100). So, I run the PJ at 40..for that particular source, which is my HTPC.
The settings are very source specific. The variation from PJ to PJ is very huge. Each PJ has been set up differently, and is used with different signals. Screen size, or placement has nothing to do with anything. It's all in the bloom and smear of the tube. Get to the break point, and back down 10 notches (if it is a 0-100 scale for contrast range).
Do not use internal PJ generated (but you can use them for the initital set-up, of course) test signals for this bloom and smear testing.. use the signal you will be viewing. Your HTPC, Scaler, Satellite box, and DVD player, etc, will all load the CRT projector differently. A setting must be 'understood' (by you..and manually adjusted, unless your PJ does this for you when you switch sources and resolutions...check for this) for each device.
Even a HDTV signal on a sat box is TOTALLY different that a 'regular' signal on the -same- sat box.
This is how you keep your tubes for a long time.