Aging Tubes Change Characteristics

Yes, tube can age- lose emission, but were you aware that the characteristics change too?

 A perfect example of this is the following true story:
 I bought a used electric organ and rebuilt it for my mother as a surprise mothers day present. (And BOY was she so surprised she was literally speechless!).

  A friend of mine was an electric organ repair specialist, and after I bought an entire new set of tubes for it he told me:" Put used tubes in it". I asked why and he said "The old tubes have settled emission wise, and you won't have to re-tune it after the initial usage of your rebuild. The characteristics change and as they are oscillators, it will need to be retuned a couple of times until they are settled in".

It does make sense. Emission will start to change and the gain change after a certain period of time.

I know I have a number of NOS MIL SPEC tubes that say on the box :" Aged 100 hours". So aging provides reliability and stability, especially in oscillator circuits.