Excess heat can shorten the life of your computer. The most common causes of excess heat are dust and dirt. Clogged vents can keep heat-dissipating air from moving through the case.
If your computer is in a clean environment, an annual cleaning should be adequate. If your computer is in a less that perfect environment, you should clean your computer more often. Always turn off and unplug any components. Liquid cleaners should be applied to a soft cloth. Never apply a liquid cleaner directly.
Wipe down the case and clear all ventilation ports of any obstructions. You may used compressed air, but avoid blowing any dust or dirt into the PC. Here's some tips for a longer computer life: