Audio Research Tube AMP Reliability

I owned the ARC D76A for 12 years (1976 - 1988) with no service issues and still going strong in a friend's system, same for the ARC D115 MKII (1988- 2000 , which I owned for 12 years. I now have the ARC VT100 MKII since about 2000 with only needing to replace the fusing resistors which protected the amp from an arching defective output tube. However the VT100 requires input 6922 tubes that are very closely matched with tight triode balances. This is needed to properly bais the input section of the amp and to ensure proper functioning of the output tubes.

In general ARC tube components are very reliable.

I forgot to comment on the reliability of the ARC preamps.
I have owned the SP9, SP9 MKII, SP14, LS2B, LS2B MKII and now the LS25 MKII and the Phono PH2. I have never had any problems with any of the preamps. NEVER!!. Currently, I leave my PH2 and LS25 on 7/24 without any service issues. The PH2 is well over 15 years in my system without any issues (albeit it is solid state).

I have owned a VT-100mk111 for 7 years and have retubed it once. I have never had any service issues with it. I also have a LS-25 and PH-5 and have never had any problems. The reason I buy ARC gear is because it is reliable.

I guess my experience is different than the majority. I had a demo ref 110 for a couple of months. Had one tube failure and the next time the blown tube took the board with it too during LOTR - ROTK. I got so scared I sold my ordered unit without even taking it out of the box. Did I like the sound yes. Would I ever go back to ARC or tube amps no.

My 2 cents.

I've owned an SP-3a (upgraded to "c") since 1974. An LS-15 since 1999, a D76 (from 1975 to 1980), and a VT100 MkII since 2002. No problems with the pre-amps. No problem with the D76. Only problem with the VT100 is one of the output tubes died, which I could determine when I checked the bias and it was very low in one channel. I could see that one of the tubes was not glowing. No other damage was done. I then replaced all the output tubes, re-biased the amp, and it's been fine ever since.
PMOTZ ; I have heard just the opposite about tube layout. An experienced electronics tech I know says that with vertical output tubes, as the tubes age, metal flakes can come loose and find their way down to the bottom of the tube, where things can get shorted. This is less likely to happen with horizontal tube layout.