Powering off vs leaving on

A friend was trying to convince me that switching my components on and off many times a day is actually worse than leaving them on. Considering the heat put out by a power amp, my instinct says power off. Am I shortening the life by doing this?
Do a thread search on this subect in the archives, it's been discussed at great length many times.
If you do switch on and off many times a day you ARE better off leaving them on.
The heating/cooling cycles DO reduce the life expectancy of electronic components.
If you need to.. turn off only the amp.
The small CD and preamp electrical use are very small at idle, so leaving them on is rather easy.
I always leave the sources and pre on at all times, and my "space-heater" amp on all the time only in the winter.
If you plan on keeping your stuff a long time, leave them on.
If you amp can't run at idle without overheating, consider a different amp! There are many well made amps on the market. If you worried about Air conditioning bills, that's another thing and a valid concern.

You do not mention whether this is tube or solidstate gear.
The amp is solidstate. I dont't believe it produces excessive heat.
Turn it on in the morning, off at the end of the day. That's better than cycling many times a day. The other choice would be leave it on 24/7. One problem with 24/7 is there can be many short duration electrical spikes a day not to mention one long one that may end your choices pemanently. Good luck.
Update- I called John Hillig at Musical Design, the manufacturer (dont know why I didnt think of that earlier). He said that he leaves his on, unless there is a big thunderstorm looming. Anyway...the D-150B is a great amp for my Thiel CS2.4. Plenty of power and current. They also have great customer service.
I never turn off any of the systems in the store or at home. Great sound is our apex and there's only one way to achieve this, total warmup.
Aroc, HiFiFarm, others -
does the "leave it on rule" apply to tubes? I leave my solid state gear on 24x7, but just got a tube preamp. Do I leave it on? or turn it off each night?

I quick acid test with tube preamps is do they have a power switch in front. If so, the designer probably meant for it to be turned on and off regularly. Most will have a standby switch. When I was younger (27 now) and home more I would leave my tube pre on standby 24/7 and switch it on anytime I would listen (which was often several times a day). Now I do most of my listening on the weekend, so I switch it off until I use it. No sense it leaving idle for days, IMO.

Actually my cartridge takes longer to warm up (4 sides of a LP) than my tube preamp and power amp take (20 minutes). So I now leave my tube gear off. I do leave my solidstate phonostage and digital gear on 24/7. I don't hear and warm up effects from my phonostage, but I do from the DAC. And it takes a full 48 hours to settle it. So it must be left on all of the time.

During the weekend, I'll put my tube pre into standby if I'll use it within 8 hours. But my tube amps I'll turn off if I won't use them within 60 minutes. No sense it burning up power tubes. But the flip side is it makes to sense to constantly cycle them on/off several times in one single day. I get 2 years out of a set of output tubes. IF the power amp is left running 24/7 I'd need a new set every 6 months. Time to get that 845 tube amp right? Hahahaha.
If a component fails because of switching it on and off too often, then it is not well design or have mediocre parts. Some examples of electrical things that switch on and off quite often that can last years (in some cases, decades) are the refrigerate that cycles on and off dozens of times a day, your TV, car, cell phone, etc. Some may say that audio components are more sensitive, then that goes back to asking, why? Maybe because that parts aren't designed to be as robust as it should be. A sensitive device that gets gets switch on and off and subjected to electrical surge upon turn on is the sensitive filament in light bulbs. But you are told on the packages how many hours to expect from them, they are designed to last only so many hours. So when I read that those that keep their components on because of fear of shortening their lives, then we really don't have confidence on their design. Buy a Bryston, turn it on and off all you want and sleep peacefully for at least 20 years.
I won't repeat any of the sage advice above except to say that I'd agree with leaving the SS on and turning power tubes on and off if you aren't using them for longer periods.

As a note of further info, should you be curious or want to try to convince the wife or S.O. that it's not too expensive - there are simple devices available to directly measure power consumption when plugged into a wall outlet. I've been using one to monitor a few of our appliances to figure out why our electric bill is rather high. The one I purchased is a "Kill-a-Watt" which costs about $35 online. Once plugged in you plug in the appliance you wish to monitor. The timer starts running as soon as a device is plugged in. Over whatever period of time you leave it plugged in it will measure the amount of electicity in Kwh (killowatt hours) that the specific device has used, and over what period of time it consumed that amount of power. You can then translate that into usage per/day/month/year/etc. and put a dollars and cents amount to the use based upon your local rates. I tested my home rig, consisting of a 100wpc SS amp (class AB/A), A DAC, and a transport. In my case I tested over a 24 hour period with typical use, and all components on 24/7. The results? With our rather expensive urban summer rate averaging around .07 cents/Kwh the entire rig costs about 13 cents/day to leave on. In contrast our fridge costs about .18 cents per day to run 24/7. YMMV widely regarding your rig depending upon just what you are running. Class A gear is going to cost significantly more to leave on. I don't think transports and DACs cost more than a few pennies a day. So if you are concerned or just curious, for $35 or less you can find out. I even came across a DIY version of an electrical consumption meter online, but lost track of the URL.

KKM, my concern was wear on the tubes and sonics. But I do not think you post was aimed at me. I agree with you. Well made gear should be expected to both stand up to 24/7 duty cycles, as well as being switched on and off.

But sometimes, even with heavy duty stuff, there is something to be said for (extra) logitivity by keeping everything "hot" all of the time.