If you want to have the best piano for the event, the sound quality is highly dependent on how well the piano is tuned. For a frequently used instrument, it is recommended to give it once every 3-6 months, and before the concert, especially if the instrument has been transferred to the stage, to keep it in good condition and at maximum levels, in order to benefit from a rich sound with superb tone.
Even if you don't use it, experts recommend at least two tunings per year, two to four weeks following the end of major seasons (early spring - after dry winter air, early autumn - after high summer humidity).
The steel utilized in the ropes loses its initial flexibility while left unused or tweaked from time to time, and can easily break when brought back to the indicated strain. The longer an instrument is left untuned or underused, the more difficult it will be to re-tune it and the greater the expense.