To Power Down, or Not to Power Down

My pre-amp (Rogue Audio 99) and amp (Cary CAD-120S MkII) are both tubed. There are days when I will have a listening session for about an hour followed by a two or three hour break followed by another listening session (or two). If the next session will be within an hour or so I leave the system up, but I'm not sure what to do when the interval between sessions is longer. My questions are...Is it better for the equipment if the system is powered down between sessions that are more than 2 hours apart, or should the system be left up? Is there a detrimental effect on tube life by cycling power up/downs in this short a time period? I would prefer to power down for simple green reasons, but the cost of eight KT88's failing prematurely would be far greater than the increase in my electric bill. I would like to know what others in a similar situation do?
Jerroot, I usually leave my system on, sometimes it will be on all day with only a couple hours of serious listening. I'll tell you, that last hour is the best. The tubes, caps etc really should not be cycled multiple times everyday. I just put the cdp on repeat at a low volume and let it play.
You do bring up a good point about leaving the equipment on. Back in the 70's when I was a tv tech, some sets had the tube filaments at half voltage when the set was off. This way when powered on, the tv would warm up and on in a few seconds instead of waiting the 30 second warm up. I figured that was how tube circuits tried to keep up with the new solid state sets at that time.
I power up the tube amps when I start listening for the day and shut the amps off at the end of the day. If I know that I am finished for the day, I shut the amps off. I try not to leave the amps on if I am leaving the apartment for more than an hour and the amps are never left on overnight.

I pretty much do what Rich does .....

If it's more than 3 hours I power down. I have a Cary CAD 120's The 3 year warranty runs out at the end of the month. I have to send it back because the right channel is out. I think a cap. Jerroot, did you have yours upgraded or buy the Mk II. I was wondering if the upgrade is worth it. I love the sound of this amp paired with a Cary SLP 98P. Your input would help thanks.
My unit was manufactured as a MKII, not an upgrade, but in the end I don't think there should be any differences between the two. I would think that Cary would do everything to make them indistinguishable from one another, but a call to them can get you an answer to that question. From all I've read, the upgrade seems to be well worth the investment. Here is a link to Anthony Cordesman's Dec. 2010 review in TAS which makes some comparisons to the MKi and MKii.

Thanks for the input, all.
Leave them on based on your post. You will wear out the tubes faster by powering them on and off throughout the day.
Jerroot, thanks for your help. Maybe I'll get the upgrade since I'm shipping it back to Cary anyway. I'll take a chance, why not Columbus did. Thanks again the article was interesting and I should be set with years again. I wonder how to keep the room cooler in the summertime, but I had a V12R and wondered how to keep the room cooler in the wintertime. The CAD 120 sure runs much cooler.
Power down its cool!!
I have 40 year old Acoustat servo tube amps that are constantly on, but the difference is that the tubes are in an idle state, not fully powered on.

This saves the tubes from the surge most other tube amps have to endure.

I don't see why this practise isn't more common in the tube community.
I spoke with Cary. It's ok to power down. Preamps don't matter as much. Jerroot, Cary suggested that since I have the SLP98P it would be better to get Cardas Caps and new Hexfreds, than to have the gain and feedback altered since the SLP98P has such a high gain. They recommended I not get the MKII upgrade in my situation. Thanks again for the avguide info.