I'm curious about listener's experiences with tube dampers. I've explored old threads but the institutional memory here is very scattered and much of it is dated. I'd love to learn what specific dampers people have found useful, if any, and the sonic benefits that result from their use as it pertains to small tubes (12AU7, 12AT7, 12AX7, 6922, etc). Do they shorten tube life? It seems as though we go to great lengths to quench spurious vibration everywhere in our systems, so why are they not used universally?