I'm currently exporting and compressing quicktime file of my 80 minute movie from an imac. From the looks of it, it shall be 10 hours process. My biggest concern is: Should the screensaver and the energysaver be turned off or on?

The new imacs tend to really heat up and I'm concerned with such a long duration of exporting, the mac may damage itself?

Can't speak to the BRAND new iMacs but my 3 year old iMac churns away on renders, sometimes for more than 24 hours for LARGE exports, without a problem. I leave the screensaver set to go dark after about an hour and I have never had an issue with waking up. I don't allow my drives to spin down though.

OSX10.4.11 on a white iMac 2.16GHz w. 2GB running FCS2 (FCP6.0.6)

Hey Phil, I run 21'5 iMac with 3.06 Intel for about 7 months and it's been handling those long 8-10 hr renders pretty stable.
Screen server - off
Display sleep - on
Computer sleep - Never
AirPort and all unnecessary apps - off
It heats up, you can cook your breakfast on it when get up to check on render in the morning. But it does not seem like a big deal. Mine sometimes stays on for 3 days and keeps rendering one project after the other.
Use and abuse, it should be fine. That's why we pay top dollar for this brand.

My bad - as Alex says ScreenSaver Off Display Sleep On is how I run... sorry for the misinformation...

I have an iMac 21.5 that is four months old. I routinely render for 5+ hours at a time. The aluminum case makes it feel hotter than it actually is. I have measured the temperature at the exhaust slot on the top rear, it never gets above 110 degrees Fahrenheit. That really isn't bad for modern circuit boards.

Jeff