"Like all chips, you want to try to keep your chips as cool as you can to increase their longevity. Personally, I’d try to keep a Haswell chip below 85 °C for 24/7 operation (definitely below 90°C); not because they can’t take more (they can), but because it’s usually safer to err on the side of caution."
HOKIEALUMNUS - Overclockers.com.
Interested in overclocking a Haswell CPU? Check out the 3 Step Guide from Overclockers.com. As mentioned repeatedly in the article, these new processors run hot.
If you're wanting to keep those temps down, consider a high end CPU cooler, liquid cooling kit and also, importantly, some better quality thermal compound.
