Piano tuning is the art of making adjustments to the tensions in the strings of the piano so that the instrument is "in tune". I consider aural and electronic tuning to be equally important. I now incorporate both aural and electronic tuning methods to make the most accurate tone. My approach to each instrument is very individual and always reflects my intuition and experience. Since I have been tuning pianos every day since 1981, my ear is well trained, and my perception and opinion are absolutely reliable. The stability of tuning depends on the professionalism of the tuner and the technique that is used.
Rapid decline of the tuning might be influenced by humidity and temperature fluctuations in your home. The recommended humidity in the house is 40-60%, and the temperature range is 18-21 C°. The other reason for tuning deterioration is loose tuning pins. The loose pins in the pin block make the piano untunable and are a reason for the repair of the instrument.
The piano should be tuned at least once a year. For better quality and stability of sound, twice a year is recommended. Professionals must have their pianos tuned before each performance or recording. Usually new pianos should be tuned 2 to 4 times during the first year.