This is the question I'm most often asked and that's because it's a very important question. The short answer would be, "As often as it needs tuned", but, that's not very helpful. So, in an effort to be more helpful, I would say, for casual home use, about once a year should be sufficient. Having said that, there are forces working on your piano all the time to make it go out of tune. The first is humidity. High humidity makes the piano go sharp (Yes, a piano can go sharp!) and low humidity makes the piano go flat. Most people don't realize that a piano is an organic instrument, like most stringed instruments. So, the weather affects it greatly. Second, the quality of the instrument can determine how well it stays in tune. Thirdly, how hard and often the piano is played. Playing it hard can literally knock it out of tune. And lastly, how well the player wants it in tune. All of these factors come together to, well, keep me in business!