If you listen 2 hrs per day, 365 days per year, you get 6.8 yrs out
of an output tube. Whilst some solid state gear might last that long
without a service, a lot do not,

No idea what percentage of what commercial designs you call "a lot".
Perhaps you could specify?

It's partially a matter of how much degradation you are willing to tolerate.
For the inveterate tube, egregious amounts of distortion are apparently
considered to be a feature, not a bug. For those of us who were into sonic
accuracy, it was kind of depressing to see our amps with EL-34 output pairs
lose 10-20% of their clean output capability within 6 months.

What an outright lie this guy tells!.

I have an amp with a pair of Sylvania EL34 that are at least 35 years old,
and it gets used every other day in my workshop for testing client's speakers,
and where I need a
low impedance source for testing crossovers.

The emission is down about 15% over new tubes but the amp still measures 0.15%
at 25 watts.

I have measured it several times since i built it 6 years ago using the second
hand tubes
I aquired cheaply, and which are expendable if they fail.
None of the claimed degradation
in the cleanliness of the power output has occured.
Many other amps that I have built and sold and serviced year later for
occasional nopisy pots, or to allow some upgrade have shown no audible or
measurable
reduction of power or increase in thd.



Enough to keep me busy repairing the darn things.

It's a business! ;-)

And I am only one of maybe 50 repair blokes in a town of 300,000 ppl.

Says something good about the actual reliability of modern electronic
components.

There shouldn't be a single failure of an SS amp in my town in any given year.

But maybe thousands of failures occur.

There is no point in arguing with Arny.

Patrick Turner.