My Yamaha C3 grand piano is supposed to be delivered in this week. While I was waiting it, I was searching cheap upright piano for practice. I dropped by one of local piano shop today. It was very small piano shop so there were only five uprights. I passed several expensive used Yamaha and tried 80s' refurbished Kawai upright then tried Kingsburg 126. I actually didn't expect much from the piano as it was made by Pearl River in China. But I was quite amazed just when I pressed some cord. It sounded just like small quality grand piano and tone was quite deep and mellow.

It was even better than Kawai K300 actually. The feel of action was quite similar to Bechstein A124.

The price was around $8,000 NZD tagged and brand new but it's still too out of my budget. Actually it sounded like grand piano more than Bechstein A124.

But as I've never seen 20 or 30 years old Chinese second hand piano, I am not sure how long they can keep the quality

Every piano will change in 20 or 30 years. How it changes depends on how it is played and how it is maintained.