Thiel Owners

@JTHIFI, those Thresholds were over engineered and built to the most conservative and highest standards, i.e. the transistors are operating at only 20% of rated output.
The only real wear concerns would be caps, power switch (a circuit breaker), feet and maybe connectors, and perhaps bias status. The caps (most expensive part) and binding posts are advertised as replaced and even upgraded.
Should you ever need service the new Threshold offers it, and I’m told Nelson Pass endorsed Jon Soderberg’s (past tech when Pass ran Threshold) Vintage Amp Repair (whom I can personally recommend) offers it as well. Just think, the amp is about the same age as your speakers and isn’t mechanical like your speakers.
FWIW, Nelson Pass seems to put a lot of emphasis on Class A output. The Threshold’s actually offer more Class A bias than the more recent comparable and even above Pass Labs models. Some prefer the bi-polar outputs bass response and lower impedance capabilities of the Threshold’s. The model up for auction doesn’t have the benefit of balanced inputs and circuitry like the Threshold e series (heck some of those e series Thresholds even hard dual tranies) or the Pass Labs claim to fame "super-symmetrical” balanced circuitry and inputs of the Pass Labs amps. But if your running through your Bluesound Node 2i with it’s single ended only outputs it doesn’t matter. Why pay for features you won’t use?

BTW, I seem to notice the price of these old Thresholds not trending down, but instead up.