And at the opposite end of the spectrum: over 20 years ago I built a passive attenuator preamp. I used the highest quality parts I could find - Goldpoint ladder attenuators with Dale metal film resistors, Cardas RCA connectors, etc. After 15 years of daily use all the connectors, switches were like new condition, perfect function with no measurable or audible noise. I expect it's still working like new, but I don't know as I sold it to a very happy buyer.
Most manufacturers cheap out and save money on those parts, because the inferior cheap ones will last long enough to get the product through the warranty period, typically 30 days to 1 year.
Your Bryston example is good too. Very few companies have such high build quality that they offer a 20 year warranty. Of course, their prices reflect this!