Love getting new equipment, hate the break-in

@sns +1 "Burn/break in is not a myth”

-correct, burn-in (accelerated aging in semiconductor chips design) is a challenging part of circuit design  process. Typically semicon-chips stabilize (flatted aging effect over time) performance after 50hrs burn-in. All involved components such as active devices, passives, and interconnects, degrade performance (age) accordingly to the stress conditions, such as voltage, current, temperature, humidity, sometimes mechanical vibrations. depending on design target, systems are designed for many years, typically five or seven years. 

I have to say, it took better part of a year for the voxativ AC 1.6 widebanders on the Pureaudioproject quintets to become  tame. Sometimes you don’t realize you have pain until it’s gone. 

@sns I think there is no use to argue with "roadcykler", he knows better than anyone. It is the fact.

Burn-in is real, for sure. But it is in your ears/auditory center. That is referred to as habituation. I challenge anybody to do a blind A-B test with a burnt-in component vs out of the box. Good luck! Re capacitor formation/degradation etc., the question is, does it matter, is it audible?

BTW: null hypothesis in statistical testing is "no difference".

A genuine new, be it OS or current production, signal tube will demonstrate improvement in performance with time, to a point upon which it levels off, relative to initial performance.