There are really 2 questions here: about 1) checkups; and 2) cleaning.
It's hard to get an objective answer on the interwebs. And realistically I can see why: everyone's different.
I guess the scientific way to establish it for myself might be to schedule a 6-month checkup, and if nothing was wrong, schedule the next one for 7 months. And keep extending the time until something went wrong and then that interval would be the best time for me. Anyway . . . .
The Mayo Clinic says
only "regular" checkups.
The NHS in Britain says
"You may assume you should have a dental check-up every six months, but some people may not need to go so often and others may need more frequent checks. People with good oral health will probably need to attend only once every 12 to 24 months, but those with more problems will need check-ups more often. Your dentist will suggest when you should have your next check-up based on how good your oral health is."
Big difference between 6 months and 2 years.
The most realistic view is here
. (Read the whole thing - there's some sarcasm.)
Excerpt: "The insurance companies like the steadiness of the 6 month recall concept. It means they have their providers, the dentists that have joined their plan, doing periodontal work for prophy (prophylaxis) fees! The insurance companies are then able to essentially reduce the utilization of the plan, which in turn increases profits. In the meantime the patient is being undertreated and the dentist is either committing malpractice or committing financial suicide.
And look at this Freakonomics blog post
Excerpt: "The evidence was mixed, at best. For example, there is not strong evidence that hygienist cleaning reduces gingivitis."
I welcome your thoughts.