There is good reason to leave a system on so as to not excessivly
power cycle it. And then we apply numbers. Amazing how numbers expose
junk science reasoning. For example, power switch is typically rated
for 100,000 cycle: seven times every day of the year for .... 39
years. IOW worry about something that is totally irrelevant.

These decrees about power cycling (thermal cycling) as destructive
are chock full of technical ignorance, no numbers, and even forgets
that normal operation is also power cycling and thermal cycling.

Semiconductors are manufactured in repeated cycles from room
temperature to upwards of 900 degrees. Now that is real thermal
cycling - and it is not destructive. Do same items get thermal cycled
when temperature varies less than 100 degree? Of course not. Yes
thermal cycling is destructive. And again we apply numbers. After how
many generations? When doing it seven times every day - including
holidays and vacation? Junk science proclamaitions must routinely
avoid numbers so as to promote myths.

Stress from power on is irrelevant. But then electronics also
contain additional protection layers that makes that power cycling
irrelevant: inrush current limiter. More information unknown to those
who just *know* power cycling must be destructive. That is the problem
with junk science. It never first learns about basic technology - even
a 1950 technology called inrush current limiter - AND completely avoids
numbers. Once numbers are provided,, then it is obvious: turn it off
when done just like a TV or radio to perserve life expectancy and
eliminate wasteful power consumption.

Nonsense about "thermal cycling" is classic "snake oil".

Meanwhile, note what was posted about light bulbs. However, when one
first learns science or even consults ight bulb industry specs: power
cycling is not destructive to light bulbs. If power cycling was
destrutive, then orange traffic signals - power cycling all night long
- would be first to burn out; would often be seen failed. Those bulbs
fail so infrequently that sometimes the bulbs power cycled most -
orange - are not even replaced by LEDs. Reality - even using numbers
from the light bulb manufacturers - light bulb life expectancy is a
function of voltage and hours of operation. Power cycling is
irrelevant. There is no formula to relate power cycling to light bulb
life expectancy. But there are plenty of formulas from real world
scientists (not junk scientists) that relate life expectancy to voltage
and hours.

Just like 'thermal cycling', light bulb life expectancy is related to
power cycling only when junk science - including no science AND
especially no numbers - is promoted. Lurkers are warned about those
who always just know - and yet don't do the numbers.

Glenn Richards is invited to cite how electronics is manufactured at
upwards of 900 degrees for multiple times - and it not "thermal
stressed". Glenn Richards is invited to cite industry science (and I
will even help him by providing the light bulb industry bible found in
any good library: IES Lighting Handbook) to cite industry science that
demonstrates a relationship between power cycling (thermal cycling) and
life bulb life expectancy.

Glenn Richards wrote:
Mike Cawood, HND BIT wrote:
My late wife's stepfather, W Cutler of Wolverhampton, read in some
mentally deranged hifi magazine that you should always keep the
system switched on, ...

Yes... when hi-fi magazines talk about leaving the system switched on
permanently... I don't think that's *quite* what they meant!

Actually there's a lot to be said for leaving your kit on all the time
(if you're using it for more than say 8 hours in a day)... it eliminates
the "thermal cycling" effect. No, this is nothing to do with snake oil
or esoteric audiophile theories. If you heat metal up to 40-50 degrees
it expands, cool it back down to 18-20 degrees (normal room temperature)
it'll contract. Enough cycles and it'll fracture.

Also it avoids the surge current when you power it up. Think light bulbs
- they nearly always fail when you turn the power on. A sudden inrush
current into a cold filament causes a thermal shock. As an aside, the
bulbs for my wall lights in my living room are quite expensive, so I've
wired them through a 'soft switch' which fades them up to full
brightness when you turn them on and fades down to dark when you turn
them off. Practical advantage is that it avoids thermal shock to the
bulbs... and it looks *really* cool!