The rule of thumb for vacuuming a carpet is once every week. However, relying solely on vacuuming is not enough to keep a carpet clean; similar to icebergs, the dirt and grime a standard vacuum cleaner removes is only a small fraction of the actual amount of dirt within your carpet. In fact, many OKC carpet cleaning experts, such as Brandon Johnson of Anew Carpet Cleaning, claim that almost 85% of the actual dirt remains hidden within the depths of a carpet. This accumulation of dirt and grime can present a variety of health hazards; many different bacteria and molds find the dirt and grime left behind in carpets to be a perfect breeding ground. Sadly, even the highest setting on your vacuum cleaner is not strong enough to remove inner layer dirt.
http://anewcc.com/2013/12/13/get-regular-carpet-cleaning-okc-cleaner-healthier-home/