Hi. The longest and still in use running the PC audio and a turntable right now just above the monitor is a Marantz 1060 Console amp.  I bought it in 1969.  So 57 years.  

Hi The amplifier sounds excellent.  They used really good components and built them to last.  The only thing I have needed to do was replace the power switch as the original got crunched.  Back then roughly 35 years ago they were easy to locate.  I think it was about $2.  Now things might be a bit more difficult.  I find that I have to exercise the switches about every 6-12 months as most never change in the settings.  I really like the amp and it mates well with the pair of Martin Logan motion 4's next to the monitor and a ML powered sub on the floor nearby.  When poking through the web on values of vintage gear this one kept showing up in the $1000 range.  It seems that is was among some of the last actually designed by Saul Marantz and built to spec in either Sunnyvale Ca or Japan.  The 1976 receiver (2250) is not built to the same standard as it was among the first built under the Superscope take over.  (my dates may be subject to question as that was a long time ago)  It sounds excellent also.  The third Marantz is a 2265B receiver.  Just slightly newer than the 2250.  Build is about the same.  This one is a world wide model and can run on pretty much any voltage.  Nice sound again, but the build is not all that great.  I have had trouble with that one.  It fried the speaker muting relay, had panel bulb issues and seemed more sensitive to needing the controls exercised.  Generally a nice unit, but not as well made.  Web values indicate the same thing you can get one supposedly refurbed for about $850.  BTW all the tube models are now out of reach by pure mortals.  Mega dollars.  Another thought.  With premium gear it is usually not necessary to re-cap them unless there is an indication of malfunction.  They were designed to last and even the  not so pretty builds of the 2250 and 2265 the components are top notch. You are more likely to screw something up than enhance the sound.