Do you think other manufacturers that release "new" product updates every 12-18 months, or worse new products because there is no upgrade path are simply offering design breakthroughs? Or is this just running a successful business?
There is something to be said for point-to-point wiring and the absence of printed circuit boards for ease of upgrade. Hand built components may have more upfront costs, especially if the manufacturer treats his employees proper. Designs that cannot be upgraded may deliver their cost savings up-front. Different manufacturers take different approaches, something perhaps better considered when you make a purchase than afterward.
Fwiw, I respectfully disagree with the above comment about AR (if that means Audio Research Corp..) To support customers of both new and used gear, they maintain a substantial tube catalog that goes well back in time. That doesn't sound like planned obsolescence to me.
The wheel of progress grinds fine and over time the chaff falls out. I want successful audio companies to stay in business and prefer manufacturers who actively seek to improve their products, whether by leaps or evolution. Without new models and upgrades, the high end is a dead end.