Reliabilty, Keeping Equipment Powered on or off?

One thing not mentioned. Power line transients. The longer something is kept on and connected to the AC power, the more potential for damaging power transients to destroy components in your power supplies. If you have good line voltage protection (like a Furman line voltage filter, for example), then this is less of an issue. But also be apprised that many line voltage protection devices (like MOVs) have a limited number of transients they can absorb before they fail and you have no further protection.

Power brown outs may create similar problems. If you have frequent or constant power line drops, this can also be hard on equipment as it shuts down due to the low voltage then re-powers as the voltage levels are restored. All this may be happening while you are gone and unaware if you leave equipment powered up continuously.

My Rowland Cadence / Coherence preamp/phono doesn't want to be powered down, in fact there is nothing in the manual about turning it off, ever. Worse, if you power it down, you have to go through a whole blah-blah to start it up again properly, vis-a-vis the batteries in the power supply, and to top it off it forgets where it was. I turn the preamp down to zero, and that supposedly shuts down almost all of the internal circuitry.

A suggestion that I have deemed to worthwhile considering is the contention that amps,,etc  are most at risk for damage when a unit is turned on.   Inrush current.    While undoubtedly there are  electrical components in place to help counter any effects of the surge --It seems to make  a lot of sense to subject units to turn on current as little as possible.     That being said-- I am not leaving my tube amps on nor my s.s. amps on especially my class A amp.  I do leave a Trends amp on as it is quite economical to run.   It is more of a summer amp.     I am leaving my 2 tuners on that are used daily---especially considering they are vintage tuners and dont want to subject them day to day to inrush current .  I listen to my systems on a daily basis.  My Sonic Frontiers Line 1 has a standby and I use that.  If I am going away for overnight or even the entire day I usually shut it off completely.   As long as I am in town  I would not want to be powering it up every day subjecting the tubes to start up current of which it is known to subject tubes to more stress .    Re/power line failures.   I think a good portion  of the high quality equipment made  and even not in the higher price range comes with protection circuits for power failures and surges.    They have to design this into the circuits --it is part and partial of designing a quality power supply.      I recently bought a pair of Emotiva mono's  and am surprised at the lengths this company has gone to in protecting the circuity for a not much money at all considering what I paid for my Pass amp on the used market.  .     I leave the Emotivas  in standby and have been using them primarily in my main system as of late.   This with a  $5k plus (new) Pass amp sitting idle.       

skiroe

I can't speak to all equipment, but I am very familiar with Parasound as I have schematics for the JC1, JC2 and other products such as the 2200ii and P3. Although well designed (as good or better than most), there is no voltage transient protection besides filter capacitors. Transient voltage protection is typically not provided by most manufacturers and is left to sand alone outboard line filter and transient protection devices.

So many with different opinions.
IMHO, i would rather deal it a more scientific way. Generally, if the measured temperature on the chassis (using a temp probe) is less than 35 degree C, it is safe for equipment to remain on 24/7. If you need to be more specific, just open up the chassis and measure the heat of the components inside (i won't be responsible for any damages to your equipment and to your own safety), if the temp of the components is hovering around 40-45 degree C, it is still OK to be on for 24/7, BUT with one caveat , you gotta search for the lowest temp rating of internal capacitors. If it is rated at 70 degree C, then the internal ambient temp and\or components gotta to be less than half of that, i.e. 35 degree C or lesser. Capacitors life span and other electronic is affected by temp and their specification rating would drift faster over time due to heat.