Does anyone leave their amp and preamp on all the time?

My preamp (Levinson 326s) and amps (Parasound JC1's) have standby modes which minimize the amount of warmup time.  I wouldn't leave them on all the time even if they didn't however.

On those voracious vacuum tube power amps…

I’m no model “Mr. Green” when it comes to conservation, but I’m sufficiently astute to recognize that some vacuum tube power amplifiers so exceed the bounds of tolerable waste that they merit special distinction. Other forms of electronic inefficiency pale when compared to tube amplifiers that use eight (or more) high power vacuum tubes in their output stages.

Listed below are basic performance claims for three closely comparable stereo power amps. One is solid state ($$$), and the other two are premium ($$$$$) vacuum tube power amps. Take a look; compare. Also, be assured that what’s shown is entirely representative of equivalent product that’s offered by other makers. Specifications are precisely as extracted from the related websites.

(1) Parasound model Halo A23 stereo power amplifier (solid-state):  Continuous full power output of 125 Watts (x2) into 8Ω, 200 Watts (x2) into 4Ω, 20 Hz - 20 kHz, both channels driven.

Total harmonic distortion: < 0.06% at full power output. (Note total harmonic distortion limit.)

Power required: 25 Watts in standby idle, 700 Watts at full power output into 4Ω loads.

Mains fuse (USA): 6.3 Amperes.

Advertised selling price: $995 ea. (per Audio Advisor, on-line site).

(2) VTL Amplifiers Inc. model ST-150 stereo power amplifier:  Uses eight 6550 output tubes. Full power output of 150 Watts/channel is cited, but the related test condition is not given.

Specified power output = 120 Watts into 5Ω. (Driving both channels is assumed, but not stated.)

Total harmonic distortion: Less than 3% at 120 Watts into 5Ω loads, 20 Hz - 20 kHz.

No power output ratings were provided for 8Ω load or 4Ω load. (Rating would decline at 4Ω.)

*Power required: 240 Watts in standby idle, 800 Watts at full power.

Mains fuse (USA): 15 Amperes.

List price: $12,295 ea. in Canadian dollars (per Melbourne Hi Fi, Victoria, Canada, on-line site).

(3) VAC (Valve Amplification Co.) model Phi 300.1a stereo power amplifier:  Uses eight KT88 output tubes. Power output of 150 Watts cited, but conditions not given. (See distortion rating.)

Total harmonic distortion: Less than 3% at 135 Watts/channel continuous average power at 1 kHz into 4Ω load when connected to the amplifier’s 8Ω output tap (stereo mode operation).

*Power required: No power consumption data is provided, but it’s likely ≈ VTL ST-150 (above).

Mains fuse (USA): No information provided.

List price: MSRP $22,000 ea. (per Scott Walker Audio, on-line site).

*Both tube amps consume more power when in benign standby than a 55 inch Sony LED/LCD TV set does in use. Consider: 240 Watts of standby consumption is equivalent to continuously burning four 60 Watt incandescent bulbs without providing any light—just undesired heat. That’s conspicuous waste—and periodic expense to replace the tubes becomes even more vexing. 

While I don't leave my entire system on all the time, I use 833-A  single ended triodes to run the bass in a tri-wired speaker system, the cathode heater on an 833-A runs at 10 amps and 10 Volts and it will not let you get away with anything but the purest DC because it hums loudly otherwise. The power supplies for the heaters need at least 4.5 Farads from automotive digital capacitors to filter out the hum. But you can't hit them with the current from the 10 volt transformers, heavy duty rectifiers, and the 0.1 Ohm dropping resistor with such colossal capacitors emulating by force and effect a short circuit. Therefore the capacitors have to have a charge maintained by 9 volt AC to DC converters that maintain this charge through 100 Ohms before you start up the system. I am certain that there are other SETs that use a less exotic triode, but once you hear what it does to the bass you never want to go back to something more ordinary and less fun.

I turn off my tube units from the back and if I don't listen for weeks I unplug them off. 

So my last out of town trip, I turned off my DAC, preamp and amps off for two days. Sounded pretty hard for about 48 hours. 

This trip I was out longer, and turned off only the DAC. When I came back it seemed just fine immediately.

My preamp is a Parasound P7, and amps are Class D ICEpower ASP designs. 

So.... yes, it seems that somewhere in those two items are things that like to be left on.