Tube preamplifier lifespan

gmcleod-

I'm quoting the OP's remark.

I still use a McIntosh C20 stereo vacuum tube preamp from the late ‘50s in my office.  First Mac pre with a glass faceplate and the last with a vacuum tube rectifier.  It’s still 100% original:  tubes, caps, incandescent bulbs.  Never needed to clean the potentiometers.  Those original Telefunken 12AX7s and 12AU7s are approaching 70 years old!  As is the vacuum tube rectifier with its soft start which probably contributes to the continued life of the capacitors.  That, and everything in there is run at a very sane B+ rail.  It still sounds great though admittedly highly colored in a very tubular way 😆. 

I wouldn't trust the opinion of someone who sells new gear about how long it lasts. 

I currently use a 20+ year old Conrad Johnson LS17 tube preamp. I actually spoke to a tech at CJ and asked them this exact question thinking I might need to have it looked over and possibly change some aging parts like caps in the power supply.

His answer, was, other than tubes that obviously need replacement as needed, my preamp, if I perceive it to be functioning well, is just fine.

The CJ LS17 runs 4 6dj8 (6922) type tubes which are likely not as heat generating as other tubes. Also I always have tube savers between my tubes and the tube sockets on the circuit board to keep the pins in the sockets pristine and keep the heat from the tubes a bit removed from the circuit board. I do this with all my tubes in my power amps as well.

To the OP- I am using a Preamp by Linear Tube audio, which claims that they run the tubes in such a way that it can last 10 to 20K hours. I had the amp for about 2 years now, its pretty much turned on 18 hours a day. 7 days a week. 

i had a spare set of NOS 12au7 and 6sn7 and tried to switch it and I have NOT heard a difference between the old tubes the spares. 

so i am just going to speculate that it may last 10K hours or more

I  beleive its the Preamps design that determines the tube life

YMMV...