that's actaully bad for your CPU, if you let it cool down regularly after being at a constant heat then it damages the chip more than keeping it going at full tilt.
The reason is because the CPU expands and contracts as it heats up and cools respectively - if this happens too much the CPU is in danger of cracking. There is no reason not to run your CPU at full usage 100% of the time, it might actually extend its life.
