300Bs - does leaving them on shorten their life?

I have NEVER heard a manufacture tell anyone to leave the "Power Valves" on.. EVER.. Then again, what do I know..

The little signal valves, I've seen stay on for months at a time..  Some designs are VERY low voltage and the valves last 15-20,000 hours..  I've not seen power valves do that.. 5,000 hours is really a push. 2-3000 is more like it..

I've never seen a signal valve erupt, and breach the glass, rectifier and power valves, I have...

What about some of the hand made valves.. 4K+ for a pair. Rebuildable.
Maybe I should start making them out of old pint and quart canning jars..

Gears are grinding...

Regards

I recall a thread posted on another popular audio forum. A ship that sunk during WW2 which had a hugh supply of Western Electric 300Bs was just brought up. This was posted on 4/1.

If a manufacturer ever recommended leaving tube gear on all the time in order to prevent damage from the act of turning on the gear, I would never buy from that manufacturer.  It is not hard for the manufacturer to put in a soft start circuit to prevent damage from turn on.  A tube is not like an incandescent  light bulb (which is designed to come on instantaneously) and it warms up relatively slowly so that it does not suffer as much from thermal shock of being turned on.  There is a potential for damage if the plate voltage ramps up too fast such that full voltage is applied before the cathode has warmed up enough to be fully emitting electrons (referred to as cathode stripping).  Cathode stripping is less of a concern if the amp is tube rectified because the rectifier itself slowly ramps up the plate voltage as it warms up.  Some amps, particularly those with solid state rectification will have a circuit that limits plate voltage until the cathode has time to warm up (my linestage, although tube rectified, has such protection).

The only good reason to not turn off tube gear when one is not listening to it has to do with warm up time.  Tube gear, like all other gear, sounds best when it has been on for a while.  The good news is that tube gear usually sounds good within five to ten minutes of being turned on, which is a much shorter warmup period than solid state gear requires.  I leave my gear on when I am taking a short timeout from listening, but, otherwise I turn it off, particularly when the gear will be unattended.

@Vineland,
Wise decision. Some people can make an argument for leaving the small low signal tubes on continuously (Although I don’t). I can’t imagine any reasonable case for keeping the power output tubes on 24/7, none. Now if your amplifier has a very low draw ’stand by’ mode that’s a possible exception.

Good quality 300b tubes have long lives (The EML XLS and vintage Western Electric 300bs have reported 40,000 hour lifespan) but I wouldn’t gratuitously waste useful tube lifespan leaving them on constantly. If I’m home all day I leave my 300b amplifiers (Mono blocks) on through out the day if  listening sessions are planned  and then shut them down at the end of the day . I do this rather than turning on and off multiple times during the day.
Charles

@vineland, 
Via another thread I discovered that you have the VAC Renaissance 70/70 amplifier. That is a superb sounding amplifier, congratulations! One of the best sounding VAC amplifiers I've ever heard and a genuine classic. 
Charles