Any good homeowner, both new and old, finds it important that they keep their home in tip-top shape. Not only because they want their house to retain value (or better yet appreciate in value), but also because an important thing for them is that their home looks as good as it possibly can. One thing in particular that a lot of homeowners have to worry about is their carpet; while vacuuming can help it in the short-term, eventually the carpet is going to reach a point where a simple vacuuming will simply not be enough and you will have to perform a deep carpet cleaning. How frequently it should be done, however, depends on your living situation.
Generally, the average homeowner is recommended that they have a professional floor cleaner conduct a deep carpet cleaning about once a year, perhaps even longer if the carpet does not get used terribly often. There are two factors that might make more frequent deep carpet cleanings advised. The first is if they are pet owners, particularly animals like cats and dogs, as they produce a lot of mess on the carpets from fur and the like.
The second is if you or someone in your household has certain allergies or respiratory issues that may be exacerbated by the presence of dust or what have you. If one or more of your homeowners smokes indoors, it would definitely be advised to do it more frequently. In any of these cases, frequent deep cleaning and restorative cleaning - anywhere from two to six months and once every season respectively. As noted above, you are recommended to hire a professional carpet cleaner if you yourself are not properly attuned to do it yourself.