I decided to test the tubes in my 300B PSET amps today since I haven't done it for nine months or so. I am using a quad set of Western Electric reissue tubes. I've had them installed in my monoblock amps since early Dec 2021. According to my Roon app, I listen to them for a bit over 50 hours/week on average, so these tubes now have over 8000 hours on them.
All four tested at 103-104% Emission and 84-86% GM on my Amplitrex AT1000 tube tester. I think that's pretty impressive for power tubes. They still sound great as well.