It's actually humorous what can be categorized as "vintage" these days. Have read where people refer to our Virus KB and Virus KC, both, circa 2002 with the former ceasing production same year the latter was released. That's only 11 years. The same "mileage" is on both my Waldorf Q and XT and incidentally, no missing teeth!
My car is a 2003, but at least in the States, a given vehicle is not considered officially a "Classic" (same as vintage) until 20 years of age and above.
In any case, it seems that you have a great point because there was a certain synth by Korg that they abruptly discontinued only a couple years ago but still sell the 61 key version of it and even with Korg being one of so-called 'big three', they ceased even having spare parts available. Recently talked to a fellow Waldorf Q owner that he had same trepidation you expressed and upon ordering his Q Keyboard, also ordered extra replacement encoders and a main board because he toured at that time but could not justify close to three grand for a 'back-up synth' and he happens to be great with soldering iron. Two years later Waldorf had gone bankrupt. However, he has never yet needed to replace an encoder or anything else. It's almost like today's manufacturing has "planned obsolesce", yet have to say the Virus and other German synths I tweak are built incredibly well.