I also leave my PC on around the clock. I don't have the screen set to turn off at any point.
If I know i'm gonna leave it, I turn it off myself.
I haven't played many hours since creating this new cache-clearing task, but so far I haven't been able to successfully create a new hard save.
However, it seems like i'm able to create unlimited quicksaves and autosaves now.
Which is completely ass-backwards to what i've been experiencing for the last few years. So strange. Could just be a fluke at this point, though.