Audio Research Tube AMP Reliability

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.

Almost forgot, I also own a PH-3SE since 2002. No problem with that either.

I own the LS-16 preamp for 3 years and never had an issue.

I owned the Sonic Frontiers Line 1 for 3 years, different story. It went into the repair workshop at least once a year without failure. After 4 failures in 3 years, I eventually got rid of it and lived a peaceful life ever since.

I can only comment about the LS-2 hybrid pre, and that little puppy has never let me down *knocks on wood*.

I had many Audio research amps and pre amps. They all worked beautifully. I blow a fuse in one once thats it.