I would consult with Cary on this one. Manufacturers say different things. The manufacturer of my amp, Audionote (uk) says that my amp should stay on all of the time. Other manufacturers say turn on only when in use.
I turn my amp off during the week when not in use, manufacturer's recommendation notwithstanding. I have concerns about the safety of leaving it on unattended for great lengths of time.
The reason recommedations vary has to do with design of amps. The most damaging time for a tube is during power up. The filament is cold. Because it is cold, it has a very low resistance. The initial inrush of current is therefore very high and results in very rapid heating. This is why light bulbs seem to only blow at the instant they are switched on and rarely fail in mid use. But, some amps use circuits that slow the inrush. A tube rectifier, because it takes a little bit of time to warm and start conducting, also slows the inrush to other tubes and affords some protection for startup abuse. Some amps tend to collect heat more than others, so being on all the time abuses other components, such as electrolytic caps (which tend to be dried out by heat), so they should not be left on all the time. For these reasons, there are no blanket answers to what you should do for all tube gear.
I turn my amp off during the week when not in use, manufacturer's recommendation notwithstanding. I have concerns about the safety of leaving it on unattended for great lengths of time.
The reason recommedations vary has to do with design of amps. The most damaging time for a tube is during power up. The filament is cold. Because it is cold, it has a very low resistance. The initial inrush of current is therefore very high and results in very rapid heating. This is why light bulbs seem to only blow at the instant they are switched on and rarely fail in mid use. But, some amps use circuits that slow the inrush. A tube rectifier, because it takes a little bit of time to warm and start conducting, also slows the inrush to other tubes and affords some protection for startup abuse. Some amps tend to collect heat more than others, so being on all the time abuses other components, such as electrolytic caps (which tend to be dried out by heat), so they should not be left on all the time. For these reasons, there are no blanket answers to what you should do for all tube gear.