Steam Cleaning or Hot Water Extraction is recommended by the majority of carpet fiber producers or mills carpet. It’s one of the rare deep carpet cleaning methods .
From a health point of view a truck mounted system is more recommended in the Steam cleaning method.
In the Dry Foam Extraction they don’t use any wet process. With this method to cleaning carpet there is: No risk of over wetting and related complications.
Nearly all the carpet manufacturers or fibers producers recommends against this cleaning method for carpet. There is risk of re-soiling.
About the cleaning frequency, your carpet should be cleaned deeply every year. Deepens on the type or amount of activity a dry or wet extraction is required every 18 month.
So,you should vacuum as often as possible.
Remember that:
Even if, Steam Cleaning is the more recommended method, you should check with your carpet manufacturer or professional carpet cleaners before choosing any carpet cleaning methods.