I see nowhere where it is not just as safe to run CCleaner on startup as shutdown.
You have seen it here already - I told you yesterday ! !
To repeat with expansion :-
It is so much safer and better to only clean
manually after due consideration of all that has been done immediately after it was done whilst you remember what you did.
This is convenient and has a SAFE default consequence of no removal unless manually invoked.
Automatic cleaning is also convenient but has a DANGEROUS default of removal unless Auto is manually disabled.
Start-up is far too late to think about cancelling a start-up auto-clean,
but if you never think at shutdown and manually clean you are unlikely to think about cancelling Auto-clean
There is no conceivable benefit to whether you do it one way or another.
Yes there is. I already told you
Clean on shut-down is far superior to clean on power up where there is more than one user profile.
Clean on Startup results in Free space being wasted on junk that could have been purged if the other profile had been cleaned on shut-down.
In addition to a waste of Free space which is what CCleaner is designed to fight,
this junk is always changing and using different sectors which greatly increases partition image backup file archives.
By providing a desktop shortcut that runs CCleaner in /AUTO /SHUTDOWN mode my daughter can easily double click and leave the computer to clean and shutdown.
This does not violate my principles, she has no Admin privilege so she cannot install anything that would use "run-once-on-startup" files etc.
24 hr rule is standard & applies to pretty much all but includes.
Is that really true ? Where did you read that.
At one time it was documented as 48 hours, not 24,
and I think I recently saw posts concerning about a discrepancy in the ACTUAL number of hours and the documentation.
So far as CCleaner GUI is concerned, the relevant check box under Options => Advanced is reading
"Only delete files in Windows Temp folders older than 24 hours"
I would not like to stipulate exactly where the boundaries are for "Windows Temp Folders"
But I can tell you that every day CCleaner will purge brand new Firefox caches as soon as I close Firefox,
even though I have the standard default "... older than 24 hours" checked, and you cannot get more temporary than FF caches.
Please remember that "older than 24 hours" does not mean what the typical citizen might think.
It is Not based upon the last "modified" or "Created" time stamp, it is last "Accessed",
and "Accessed" not only refers to reading the contents,
it also refers to when the file name was presented on screen by Windows Explorer.
I have seen two different moderators recommend un-checking this "24 hour" check box for people who wanted to remove what was often accessed just because that is the way the Windows is, and NOT because any information was obtained from the file.
These people would be victims of a Fully Automatic Clean regime that assumes no other deviations from a normal configuration.
EDIT - P.S.
If you do it on shutdown, shutdown takes a moment longer, whereas on startup, startup takes a moment longer.
Agreed, but is that relevant ?
I wake up and get civilised in the bathroom, etc.
Eventually I turn on the kettle then the computer, and by the time I have made instant coffee I have logged onto the computer and can do what I want, I do not have to wait for CCleaner to clean junk because that happens at shutdown.
I am at the computer because I want to use the computer and I WANT IT NOW.
It would be intolerable if CCleaner was to make me twiddle my thumbs waiting for it to do its thing.
When I have finished with the computer then, unless I am finalising an installation,
I just double click for CCleaner /AUTO /SHUTDOWN mode and
I do not twiddle my thumbs waiting for CCleaner to do its thing - I trust it to do what it is told without me watching and waiting.