One way to find out how they'll hold up is to stick a set in an amp that has really high plate voltages like an old Orange or a Laney Supergroup.
Although I've not yet had any issues with the EL34B's in my Diezel, it would be cool to have yet another good choice for tubes. --Hopefully they don't have the reliability issues like you've been reporting with the EL34B's.
Part of the reliability issues may have to do with the relative inexperience of the workers producing the tubes. I'm sure that a lot of the western European and North American workers had many years of experience producing high quality tubes, while current Chinese workers and a lot of the current eastern/central european workers simply don't have that experience and the experience of a culture of years of quality control to draw upon. --Hopefully these tubes are an indicator of positive change.
