I wonder if this is part of the reason why your piano doesn't need more work.
When I bought my piano, it was about 20 years, the previous owner was the only owner. But he didn't take very good care of it, and it was obvious that he hadn't had it tuned regularly. (I had to convince him to get it tuned before I bought it so I could evaluate it).
After I had it for about a month, I had it fully regulated and voiced, and it was amazing the improvement. I've now had the piano for about 7 years, and I have it tuned twice a year -- not because it goes out of tune, but because I like how it sounds better that way. It sounds great, is incredibly stable, etc. I imagine that this regular tuning makes a big difference, beyond just the "freshly tuned piano" sound.
Obviously, a piano of the quality of an M&H BB is just such a good piano, but I'm convinced that taking care of it meticulously like that makes a huge difference as well.