Some pianos go up and down in pitch together and stay relatively in tune. The bass stays in tune and the middle goes up or down and creates bad octaves. Playing the piano, especially heavy playing can tend to knock the unisons out. The unisons are the tuning of the three strings for each note. I play heavily when I tune, but constant heavy playing will cause the piano to go out of tune sooner.
Some people are sensitive musicians and hear the piano going out of tune much sooner than others.
Pianos go out of tune very gradually and only you can determine when the piano is out more than you can stand it. Sometimes people hear voicing problems that have developed and interpret that as going out of tune. They just know that one note doesn't sound right. If you are a beginner and mainly playing one note at a time, you may be able to go longer between tunings. Certain types of music show tuning problems more than others.