IME, tube life may be technically correct as stated, but it is the definition of the end of life that can sometimes seem to be at variance with the manufacturer's claim.
It's why I have always recommended that my clients keep a complete set of replacement tubes on hand. Not just for the occasional emergency replacement, but to try out after 6 months-to-a-year to see if new, unbroken-in tubes have more vitality & life, especially in the areas of dynamics, presence & tone.
For myself, I have rarely heard a set of tubes - especially output tubes - that couldn't be improved upon by a new set after a year or so (assuming "normal" use), sometimes after just 6 months. The original tubes may still test ok, but they may not sound better than an unused tube.
I've never said this in a forum, but in one that is tltled, What's Best, it seemed OK to stick my neck out...
Best,
Jim
Jim,
Can you translate your "year or so" in hours play time?