I was concerned about using my iMac 27" Corei7 under heavy load for long periods of time. As an experiment I bought a small electric fan designed for people who wanted to keep cool at their desks in their offices. I pointed it at the back of the iMac while it was under load and monitored the results in temperature monitor. During the middle of the experiment I turned the fan off and then back on. Take a look at the temperature reduction as a result: Your mileage may vary but it is pretty obvious the machine is under less heat and thus less stress as a result. It hardly makes a sound at all and seems to reduce the temps a noticeable amount. One more thing: Please note that the extremely high temperatures at the very beginning of the left side of the graph were as a result of me keeping "long term values" history selected in temperature monitor and the very high temps are from my old Mac G5 computer - temperature monitor apparently migrated those temperature recordings when I used the migration assistant to copy my old boot drive from my G5 to the new iMac.