Two good relevant comments above [MENTION=49196]Repack Rider[/MENTION] and [MENTION=388729]Marcus_Ti[/MENTION]. Piano's require regular TLC including tuning every 6 months. Even then, they may need to be "regulated" after 20 years or so. Then they need to be broken in to return to their former glory. Humidity control is the most important variable to maintaining the value through sound. The wood is simply furniture. Nice wood does not a good piano make.

My wife has a 6ft Yamaha C-3 conservatory grand from 1978 that sounds great after all these years. Like bikes, they are all a bit different, even within a model run. its been tuned every 6 months from the first day. Tuning took very little time because it held so well between tunings, so the variation of tuning was small. It is important to keep the tension of all those strings close to audible spec. to ensure the rest of the supporting hardware keeps its "set".

Prior to the C-3 she had a cheep spinet, it worked for a year or so then became a POS, impossible to keep in tune for more than a couple of days. Poor maintenance was the biggest factor. Quality of design and parts was the next.