Tube rings for power tubes?

FWIW, I use the herbie's tube dampers on the KT88's in my Cary SLI-80 with no problems. Herbie sells a version specifically for high-heat output tubes.

Another vote for Herbie, his rings are very reasonably priced and graded for tube heat. I have had no problems on my 845's and what gets hotter? I am sure someone will tell me.

Well if you guys say so ;--) I have to admit, it's been awhile since I've dealt w/ a lot of hot output tubes (16 x 6550's !) so maybe Herbie is able to offer something more heat resistant than used to be available.

But I still can't understand why one would need dampers on a power output tube -- i.e. unless the tube has internal damage, microphonics shouldn't be a problem in a reasonably vibration-free environment, and adding dampers to the glass envelope would impede cooling and create hot zones. So what would be the benefit? Am I missing something?
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FWIW, I'm with Nsgarch's posts re his actual experiences and the requirements of power tubes, although I've never used Herbies and my power tubes were all common pentodes. No microphonic problems to solve in the first place.

Be sure to try them both with, and without the rings. I found that the life got sucked out of the music with rings on my EL34's.

Herbie's are probably the best out there for tube dampers that don't kill the music, at least on small tubes.

Enjoy,
Bob