I've been running tube amps for over 20 years now...
I prefer the sound of a good tube amp any day. For reliability, then power valves cause the most trouble. It depends on the manufacturer, I think. All Russian types I have tried are VERY reliable, but other Eastern block valves are not... for example I put up with the Tesla Vrsovice KT88 in my Air Tight, even though they were really expensive AND unreliable. Reason? They sounded WAY better than any other KT88/6550 I tried.
Most NOS power valves from US manufacturers are very reliable too.
Anyway, even if one goes, what is the problem? Just plug another one in. Can been done in less than 10 seconds. How in ANY WAY is that a hassle?
The best sounding valve I have tried is the 211 by a big big margin. At least for driving MLs. But some 300B designs sound awesome driving high efficiency speakers. You can also change the sound of the amp quite radically just by changing the output valve manufacturer. This is one of the big advantages over solid state. Bored with the sound? Change the valves. I do so quite often!
