Cuwatch1, my VS115 has just crossed 300 hours... and I assume you are asking about the overall sound quality vs tube life (per Soundoc)? I'm just returned to the high end, so don't have the vocabulary or recent experience of owning other high end parts, but as for "my" VS115 the sound changed radically after about 200 hours. When I first installed the amp I was a little freaked out -- the base was boomy, and the sound was conjested and everything just seemed "off". I almost took it back for a Ref110, but the dealer advised just letting it cook by leaving it on for a week 24/7. That made a huge difference - things started to sound pretty damn good and overall the sound seems to be coming more and more into focus.