There is a lot to consider with this question. A short while ago, I produced a video:
I explained how some 100+ year old pianos that have lived in a stable environment in regards to temperature and humidity, barely played, yet serviced on a regular basis can be like new! The flip side of this are pianos that live at the beach and get rusted out, or pianos in the desert with cracked soundboards. There are also pianos from schools which are worn out after just a few years. But there is another element to this.
There are certain eras of production of specific piano companies that are known for being either particularly stellar years of production, or conversely, years where quality was not up to par. However, this isn’t to suggest that every piano from a good period of production is a gem and every piano made during a lesser period of production is a dog. It’s more of a law of averages. Even brand new pianos of the same make and model have unique characteristics of sound and touch.
There are other things to consider. If a supposedly good period of production was many decades ago, it calls into question where the piano has lived, how much wear there is, as well as any major work that may have been done on the piano and the quality of the work.
You also have to consider that some piano companies have improved over the years. For example, there are many Chinese piano companies today making good pianos that didn’t even exist just a few decades ago! Even Japanese pianos were not up to an export quality of production until well into the 20th century.
So, the age of a piano matters, but it is a more complex subject than you may have thought. You are always welcome to contact us here at info@LivingPianos.com for answers to any of your piano questions! Robert Estrin 949-244-3729