The only "tube" amp I don't mind leaving on and running idle is my Millet Hybrid. I have 2-dozen tubes on standby/backup, and they all sound very similar and are easily inter-changed. The 14.4V automotive tubes in this circuit last forever. But even then I dont make it a habbit.
I have left my Earmax on/idle before a few times, but I dont regularly do that. Amperex/Bugleboy, Telefunken and Sylvania gold pin tubes aren't exactly cheap.
I DON'T leave the DV337 on unless I am listening to it. The TS tubes in this amp are my most costly. One good thing is its a dual-mono circuit, with separate L/R volume pots. So there's no easily detectible advantage in costly tube-pair matching from L to R. Sellers almost always charge more for matching services.
Regarding warm-up times yes its one of the drawbacks, and it takes some getting used to. Some tubes are microphonic and "unstable" (for lack of a better term) when they are not warmed up and have not reached steady state, so there can be (depending on the tube, amp, cans...etc) an element of risk listening to them while cold or leaving headphones plugged in while they are warming.
(IMHO) A well designed/stable tube circuit design should be able to handle on-off-on-off cycles of 15 minutes each... I mean it shouldn't "blow up" anything, nuke itself with bad "tube voodoo" in the process. But its a given, that tubes DON'T like this kind of treatment. If done repeatedly, its a recipe for shorter tube life. I have NEVER heard/read cases where repeated power cycling is good for tubes in any way.
Edited by kramer5150 - 5/11/14 at 11:24am