Leave tube amps always on?

Tubes do not "use" more energy at turn on or turn off.  That is NOT the basis for concern with turn on causing more damage to a tube than leaving it on constantly.  The concern has to do with two different issues.  The first is the stress from thermal shock.  When a cold tube is suddenly heated, the elements that are heated are stressed by the sudden heating and expansion.  That is why light bulb most often fail at the moment the light is switched on.  Tubes are subject to some thermal stress, but, it is not nearly as severe as with a light bulb.  Tubes are not made to heat up and start working as fast as a light bulb has to heat up and emit light. 

The second issue is what is sometimes referred to as cathode stripping.  If high voltage is suddenly applied to the anode before the cathode/heater has warmed up enough to be emitting electrons, the pull of the anode trying to attract those electrons can damage the cathode.

In a properly designed amp, the current should be applied slowly enough, and ideally, first to the cathode/heater circuit, and ramped up to avoid either concern.   Some tube units have such "soft start" circuits and utilize a relay that delays full power to the anode side of the tube.  My headphone amp has a circuit that takes a full minute before warm up is complete and the amp is operational.

aj,

Whether turning a tube on & off or leaving it on, a tube doesn’t consume any more power than they are designed to consume (as long as your amp is functioning properly and biased correctly). But the initial temp change from cold to hot when powering on is what is especially stressful on tubes especially power tubes.

Your LTA amp is designed to be less stressful on tubes thus longer life so I wouldn’t be as concerned with your amps. I would treat it like a preamp. Turn it off when you leave the house or go to sleep. Other times use discretion.

PS. EDIT: What Larryi2 said above while I was typing.

Nobody leaves tube amps on all the time turn on 1 hour before listing is enough.

@1extreme 

@larryi 

Thx, super helpful explanation and information. A very knowledgeable forum. 

BS, it absolutely does not cost you more energy to turn your tube amps on an off relative to leaving them on all the time. Tube life is shortened but not as dramatically as you would think. I do know some people who keep them on because they hate waiting for them to warm up. They are also filthy rich and could care less about tube life. Some tube units like my ARC phono amp have low power standby modes. I do leave that on continuously. I have a class AB SS amp in the workshop that I leave on all the time but the JC 1's in the main system are turned off.
Turning the tubes on and off stresses the filament due to expansion and contraction of the metal with the extreme changes in temperature. Same for transistors although the temperature changes are not as extreme.