Hats off to OP--great topic!
I just gave away 2 x RM9 tube amplifiers, ~44 yrs old each.
The oldest thing in my current system is a pair of KEF 103.2 speakers, large sealed 2-ways (44 or 45 years old). I remember a college friend being given a pair of these when he graduated med school. They were super-expensive for the time, ~$1,500.
Years ago I gave my brother my circa 1977 Pioneer receiver, a beautiful silver thing with pretty lights. I had it repaired once and so did he. His widow still runs it every day.