the cooler a chip runs, the longer it runs, however there are certain windows temp ranges that it is expected to run. If you do a bit of googling, and possibly figure out what the chip number is, you might be able to find the range.

I do know those G5 iMacs run a bit warm, as evident by putting your hand at the vent, you can feel the warm air, and frankly, Apple jam-packed that sucker in tight with little room I am surprised all of them just have issues with Caps.

I would have thought the screens would have had issues from the heat as well. Those G5s run hot, even hotter than the last G4's on the Powerbooks (Man those got warm) and my MacBook Pro seems to get hotter than the G4 systems (Early 2008/2.5Ghz) so they just seem to be getting hotter...