Old Piano? Pianos made before about 1900 can be good to look at, but very difficult to tune and impossible to keep in tune. Often they will go out of tune during the tuning process, or the next day, or within a few days. Pianos built in the Victorian era might be “Untunable”.
Piano not been tuned for more than 2 years? Pianos should be tuned every 6 months to maintain them in optimum health. Also, when regularly used, a piano which is out of tune will spoil the player’s sense of pitch. If your piano has not been tuned for more than 2 years then it will need two tunings, a few weeks apart, to bring it up to concert pitch.