How often is a visit to the dentist necessary if you don't have a problem?

I recall dental visits used to be once a year for a cleaning and check up. Now 6 months seems to be the norm and most dentists are pushing return visits every 4 months. Is this just a business strategy or is there a valid reason for the shrinking timeline? I don't have dental insurance and exam, x-rays, and cleaning can cost $150 to $200 each time.
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You need to go every 6 months. I'm actually a dental assistant. You can build up a pretty good bit of calculus on your teeth if you don't have them cleaned as often as the dentist suggests. Some people get a thicker build up than others. It may cost you some money out of pocket, but I think you'd like to have your teeth in tact for as long as possible. X rays should only be done once a year (bitewings). Unfortunately there are some clinics that try to "nickel and dime" their patients. Usually the 3 or 4 month recalls are for patients with periodontal (gum disease) problems. Hope this helps somewhat.
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