Simone, I, like you, am almost maniacal with my pianos. I am convinced that "domestic" instruments must be even more high-performing because it is precisely on these that the touch is refined; during performance, one can even "compensate" for some problems (the brain easily adapts, for example, to a note that is slightly more ringing than the others by adapting the touch specifically on that note). If these compensations can be an asset for the pianist during a concert, they can lead to imbalances if they occur daily at home. Intervening "aggressively" on an instrument neglected for years is difficult, and major mechanical overhauls can also leave the owner dissatisfied. It is better to intervene gradually. Even a major intervention, such as replacing the hammer rail, can be greatly "simplified" if the mechanics function well overall. In Italy, there is a lack of culture regarding taking care of one's own piano. I see concert pianists of a certain caliber with high-quality instruments that are in really bad shape. It is useless to own a Steinway if you are unable to maintain it, if it is full of friction, if it is not tuned, or if it is not constantly tuned. It is much more rewarding to play on my modest Pleyel/Schimmel grand pianos or Kawai uprights, but in more than decent condition, constantly maintained by myself and reviewed by a technician on average every 6 months. I am equipped with Teflon and occasionally recheck the friction. If I can tighten or loosen a spring, I do it myself; this is certainly not about regulating the action, something I do not presume to be able/know how to do, relying solely on the high competence of a technician. I have encountered two categories of technicians and two different responses to my fastidiousness: those who tried to avoid me or called me presumptuous (I was even told to get a digital piano if I want the instrument to always be high-performing); my current technician ENJOYS (in a positive sense) my requests, being sincere even about the limits the instrument can reach (for example, he said right away that mine is a very beautiful instrument, with a nice hammer rail, a nice action, an excellent soundboard, a beautiful sound, but that I have to deal with a good weighting but not as refined as, for example, Yamaha, and with string length and gauge that are nonetheless those of a grand piano and not a concert grand). All pianos have strengths and limitations (let's not call them defects), but taking care of them allows one to enhance the former, making us almost forget the latter. Unfortunately, most pianists do not even know how the piano action works. When I approach the instrument, the first thing is to understand where the hammer trips, with what force it is escaped, and with what it remains suspended; but if one does not know these things....
We must only be careful, however, not to become obsessive. This doesn't mean not being fastidious, but being careful that this characteristic of ours doesn't make us lose sight of the music or make us become—I use a medical term—hypochondriacs regarding the instrument. Or perhaps, instead of letting ourselves be overwhelmed by the sound, we fossilize on a single out-of-tune note, etc. When you play, you play...