There are so many factors to voicing. Hammers can be cleaned reshaped and hardened as well as softened. With the case of your Weinbach, the hammers may have picked up a lot of surface crud as well as the strings aging, sometimes even corroding, it lost that brilliance it once had. I had to restring a Steinway S that was only 20 years old because the owners lived right by the ocean and the strings corroded and sounded muddy. We have to remember here, there is a difference btw warmth and muddy, brilliance and tinny or glassy. Stability is another issue dealing with tuning and strings developing their memory. Again, pianos environment will have most to say about how your strings are going to sound. Smoke, dust, moisture, temp., salt, etc. etc. play a major role in how your piano is going to sound and how long it will last.
But of course the dealers tried to sell you a new piano. That's their job and pianos don't exactly fly off the showroom floors. There are average 2 cars in every driveway and not even 2 pianos an the whole block.
Your technician is right. Having a good piano revoiced or even restrung (about 2k) is well worth the cost.