Leave tube amp on all day?

I've just purchased my first piece of tube gear, a Cary SLI-80 integrated. What's the best for tube life? Leave it on all day or turn it on only when it's used?

On days I'm home, I may listen an hour in the morning and a couple hours in the evening. If I leave it on all day, to get 2-3 hours of listening time, it'll be on for 12+ hours. This means the power tubes won't last more than a year? If I turn it on and off 2 to 3 times each day, will the tubes last longer?

If it's best to just leave it on all day, then is it advisable to leave it on over night as well for multiple days? Turn on Friday evening and turn off Sunday evening?
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.
As Larryi suggests I would consult with cary and get their recommendation. However, I for one would not leave a tube amp on all day even if it wasn't unattended. If you are listening for short periods of time in the morning and then again in the evening I would turn it off between sessions. I would not even think of leaving it on overnight or over the weekend. The reasons being is tube life, as it will shorten if left on, but more importantly for safety reasons.Tubes can and do short out which could cause a fire especially if left unattended.

Chuck a Little over the top, I would saayLeave it on and donrt be so paranoid. Its consumer electronics, not garage gear
I just simply would turn it on and off. Unless you use cheap tubes. That's what will cost you. The rest of the amp even if you shorten it's life should last 10+ years under bad conditions.
If you're going to be using the amp for the majority of the day at various times, leave it on in standby mode. If you aren't going to use it for very long each time and / or have extended periods between use, turn it off and on as needed using your own judgment.

Tubes deteriorate with use, even in standby mode with most designs. Not only that, but some tubed amplifier designs can become hazardous / start on fire when a tube fails. As such, i would not leave tubed amplifiers on and unattended for extended periods of time. Obviously, this is my point of view, so take it for what it is worth.

I say this because most properly designed tubed circuits with reasonably strong tubes stabilize in appr 20 - 30 minutes of use. There is little to no sonic benefit in leaving a tubed power amp fired up 24/7 other than the reduction of in-rush current to the tubes.

Bare in mind that i'm talking about output level tubes here, NOT line level tubes such as found in a preamp, CD player, DAC, etc... The voltage and current levels found here are MUCH lower, hence leaving them fired up is far more benign with less potential for major problems. Sean
Some tube equipment has a mode where only the filiaments are left energized, perhaps at slightly reduced voltage. It is always desirable to turn on filiaments before gradually bringing up plate voltage, but I don't know any audio amps that are this sophisticated.

Better to be safe than sorry. But then again that is just my opinion.

Thanks all for your responses. Looks like turning on/off the amp 2-3 times on days I'm home won't shorten tube life more than leaving it on all day from what I gather here. At least that saves on electricity.

I wish there was a standby switch on this amp, as I would use it but unfortunately, it's just on or off.

Tube shorting? Ouch. It never occurred to me that was even a possibility. The amp has fuses, so I assume that would go before there's a fire hazard? Man, don't tell me everyone who has tube gear has a fire extinguisher next to their equipment rack. :-)
Welcome to the SLI-80 club. Its a great amp. If you search the FAQ's at Cary's website (CaryAudio.com), they offer their advice on this issue. My recollection, in a nutshell, is that Cary advises to turn the amp off if you plan to go more than a few hours without listening. On CDP's, they suggest leaving them on 24/7. I find that the amp heats up pretty quickly and I haven't noticed any significant improvement in leaving it on for long periods. So I just turn the amp on as needed. My CDP (Cary 308T), on the other hand, seems to benefit from being left on. I usually compromise and turn on my CDP on Friday evening and leave it on through Sunday evening, since I do most of my listening on weekends. During the week I turn both the amp and CDP on as needed.

Enjoy the amp!