Piano Tuning Recommendations By Manufacturer
“While pianos generally fall into vertical and grand model categories, each manufacturer selects its own materials and utilizes its own unique scale and furniture designs. Every piano requires a different level of maintenance, depending upon the quality of materials used and the design and level of craftsmanship. Manufacturers can provide general advice on tuning frequency but your technician can give specific recommendations based upon your usage and locale."
Here's what some of the major piano manufacturers recommend:
Baldwin Piano Company (also Chickering, Wurlitzer)
Professional service is the key. In the first year, the National Piano Manufacturers Association recommends that you have your piano tuned four times. This is a period of environmental adjustment for a new instrument, and proper attention is important.
After the first year, the piano should be tuned at least twice each year, depending upon the frequency of use and atmospheric conditions. Contact Artisan Piano Services to schedule an appointment with our professional technicians to perform this service.
Kawai Piano Company
Quality pianos demand quality care. Fine pianos require regular maintenance in three areas: tuning, action regulation and voicing. Tuning is usually required more often than the other service areas, but all three should be a part of any fine piano's maintenance. Due to string stretching, settling, and the effects of climate, a new piano should receive at least four tunings in the first year. After that, the type of use and the location of the piano will dictate the number of tunings required, but Kawai recommends two tunings per year as a minimum.
Pearl River
Changes in temperature and humidity, the amount and type of use it gets, and the musical requirements of the owner will determine how often your Pearl River piano will need service. In general, Pearl River recommends that your new piano be serviced four times the first year and twice a year by a qualified piano technician.
Samick Music Corporation
(also Knabe, Kohler & Campbell, Conover Cable, Bechstein & Sohmer)
The careful selection and installation of the highest quality tuning pins, string, and pinblock materials assures excellent stability. Regular service by a qualified technician will assure the continuing pleasure that comes only from a properly tuned and regulated piano.
We recommend two to three tunings the first year and a minimum of two tunings per year thereafter. Avoid placing your piano where it will be exposed to extreme heat or cold, moisture, or direct sunlight, all of which can cause unstable tuning, warpage, and finish damage.
Schimmel
Your Schimmel piano should be tuned and serviced only by qualified professionals. Questions regarding tuning can best be answered by your local piano technician. As a rule, a brand new piano should, depending on its location and climatic conditions, be tuned two to three times in the first year or two. An instrument played often and intensively could require additional tunings.
Steinway & Sons (also Boston & Essex)
Your Steinway piano was tuned many times before it left our factory. It was tuned to and should be maintained at A440 pitch. This is the internationally accepted standard and the standard for which all Steinway pianos are engineered. Unfortunately, no matter how expertly a piano is tuned, atmospheric variations and the nature of the piano's construction constantly conspire to bring it off pitch. 
Your Steinway has been designed and built so that in normal use and under normal conditions it should need only periodic tuning. We recommend that your technician be called at least three or four times a year. You, however, are the final judge and should have the piano tuned as often as you think necessary. To put the matter of tuning into perspective, remember that a concert piano is tuned before every performance, and a piano in a professional recording studio, where it is in constant use, is tuned three or four times each week as a matter of course. Tuning is an art practiced by skilled professionals and under no circumstances should anyone other than a professional be allowed to tune your Steinway piano.
Yamaha Pianos
New pianos should be tuned a minimum of four times the first year to compensate for the normal settling that takes place. Subsequently, as a matter of standard maintenance, a piano should be tuned at least twice a year. Of course, some musicians will choose to have their own piano tuned more often to satisfy their own personal musical requirements. When your piano needs tuning, consult your authorized Yamaha piano dealer or give Artisan Piano Services a call to schedule an appointment with our professional technicians.
Young Chang America, Inc.
(also Pramberger & Bergmann)
Piano owners will receive optimum performance from their piano if it is properly serviced during its lifetime to compensate for the effects of environmental conditions and use.
Due to the natural elasticity in new piano strings, we recommend that your instrument be tuned two to four times the first year, twice the second year and a minimum of once per year thereafter. Of course, you may choose to have your piano tuned more or less often to satisfy your own personal requirements.
Ask your piano technician to also inspect the action and mechanical parts of your instrument along with regular tunings.”
Quoted from the Piano Technicians Guild article: How Often Should My Piano Be Serviced?