Tube amp on/off: best practice?

Generally speaking, unless a tube amp has a sentry circuit that automatically shuts down tubes in the event of tube failure (very few tube amps have such a circuit), it is not a great idea to leave a tube amp unattended, as the above posters are correct - output tube failure can resemble the 4th of July in a worst-case scenario. My tube amp has a sentry circuit and I generally leave it on all day, and at times unattended, if I intend to listen at various times during the day.

Regarding the specific question of whether tube life in tube equipment is best extended by 24/7 operation or turning it on and off, this subject has been discussed in great detail in many threads. The short answer is that tube power amps should be turned off when not in use because output tubes (the big tubes) pass a lot of current, which is hard on them (cathode stripping). The answer for small-signal tubes (i.e., the little tubes found in preamps, DAC's, and the little driver and splitter tubes found in tube amps) is more complicated, but I generally advocate leaving them on 24/7. This very recent thread about two high-end preamps includes many of my thoughts on the subject, as well as those of the founders of Atma-Sphere and BAT, but you need to read through the entire thread because the discussion of how best to extend tube life is not the actual thread topic:

http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1282891541&openfrom&1&4#1

Turn tube amps of when not using them in general. If you're going to space listening sessions by 30 minutes or so, best to leave the amp on. Tubes have a finite life. In a perfect world, you'd leave them on all the time...but it's not a perfect world.

Sequence- in "Get Better Sound," Jim Smith is pretty emphatic about "amplifer ON last, OFF first." Something about getting any junk out of the system by turning tube components other than amps on first and off last.....

If you lose a tube while you are out, the speaker may get fried. Jallen

I agree with Elevick completely. I've had many tube amps over the years. One of which had a output tube go bad. Music was not playing, but there was a god-awful screech coming out of the left channel, then I saw a red flame shoot up through the top vent, followed by smoke. Thank god I was home. I lived in a condo and I don't want to think what could have happened to the seven other families in the building. I've been using digital amps for a while now.

ok, so here's another reason I don't want my lovely wife reading Audiogon.

Thank you guys for the reality-check.