I think that perhaps it would be close. Certainly more than 20 HRS, but, since you're talking tubes, which have to be replaced, I'd just let it break in over time, and not leave it playing 24/7.
I've heard that Transformers and power supply parts sound best after many years of use. Don't sweat it. Your amp will sound loads better than a SS amp right out of the box!
have fun...
Joe
I've heard that Transformers and power supply parts sound best after many years of use. Don't sweat it. Your amp will sound loads better than a SS amp right out of the box!
have fun...
Joe