Pianos that are prized by their owners need to be tuned regularly. Domestic pianos need to be tuned at least once a year but more often if played regularly.
Piano’s, like all mechanical things have a limited lifetime. The piano is a complex, high tensile, wood and steel creation, affected by most external factors.
When considering the purchase of a piano it’s good to keep in mind that pianos need to be seen and touched to determine its quality and to get a good feel for it.