Funny you should ask. I bought a matched set of the winged C's about a yr ago. One just failed with light use. I guess that can happen to any tube at anytime though. The sound of the tube is nice; rich and full. I have all my 6Ah4's I need but guess what? They too are creeping up in price. I didn't realise they were used as much as they apparently are. What happened to Guinevere; you don't use that amp?