> Keep them running [...] Bearings will last longer; they might also seize up if left stationary for too long. Likewise the drive motor.
All HDD failures I've ever seen in person (5 across 3 decades), were bearing failures, in machine that were almost always on with drives spun up. It's difficult to know for sure without proper A-B comparisons, but I've never seen a bearing failure in a machine where drives were spun down automatically.
It also seems intuitive that for mechanical bearings the longer they are spun up the greater the wear and the greater the chance of failure.
I think I have lost half a dozen hard drives (and a couple DVD-RW drives) over the decades because they sat in a box for a couple years on a shelf (I recall that one recovered working with a higher amperage 12V supply, but only long enough to copy off most of the data)
All HDD failures I've ever seen in person (5 across 3 decades), were bearing failures, in machine that were almost always on with drives spun up. It's difficult to know for sure without proper A-B comparisons, but I've never seen a bearing failure in a machine where drives were spun down automatically.
It also seems intuitive that for mechanical bearings the longer they are spun up the greater the wear and the greater the chance of failure.