How Often Should You Clean Your Floors?
Floors should be cleaned at least once a week. If dirty shoes are walking on your carpet every day, you should vacuum every day. Although this is probably not possible in an office work environment, you should know that small dirt and rock particles can cut the fibers of carpet, making it appear dirty. This is part of the reason your high-traffic areas will look worse than other areas of the carpet. Even if you have your carpet professionally cleaned, the traffic areas may still look darker.
It is also recommended that you have your carpet cleaned annually. I recommend The Rug Beater. I personally know the owner of this company, and I know that she and her staff are well educated in caring for carpets.