EDIT: Just realized somebody is practicing thread necromancy.
Originally Posted by evilghost
I own a 42" Phillips plasma, I've played Halo 1, Halo 2, and tons of other games as well for long times on end. The screen will periodically shift to avoid burn-in but after gaming on a black screen with no signal the HUD is still visible. Watching TV for about 30 minutes or leaving it on a grey screen fixes it.
Burn-in often results from uneven aging. A plasma screen will eventually fade over time due to the phosphors eventually wearing out. When some wear out faster than others, which static HUD's will cause, that will cause the "burn in" effect that you notice.
This means that you don't have to leave the HUD on the screen for 2 hours at a time for it to happen. You can have it be on the screen for 5 minutes, not show for 1 minute, and then be there for 5 minutes, repeating ad-infinitum, and that image will eventually become permanently embedded on your screen because those particular pixels have aged (from use) in a particular way compared to the rest of the screen.
Granted some plasma screens are made with phosphor material that is a bit more robust than others, this effect still cannot be avoided because you cannot change the fact that the phosphors do age, it's just the nature of plasma technology.