Pros and cons of enabling “Put hard disks to sleep when possible?” I'm not big on saving electricity at all and I'm trying to decide whether to select Mac's “Put hard disks to sleep when possible.”

What are the pros and cons of doing so?

For example, can I expect the hardware to last longer by keeping the hard disks on 24/7 versus putting them to sleep?



I'm using MacBook Pro (2017) running Sierra (10.12), but question is also interested in other (future) versions.

And why is “…hard disks…” plural when there's only one?
Advantages: 


on older traditional rotating disk drives it will save some power
on the same type of drive it often parks the heads making it less fragile in cases of unplanned moving/shock/drop


Disadvantages:


rotating hard disk drives will live shorter due to the fact that it’s the starting and stopping that kills them, not running idle
slower initial access to the disk as it starts after it was put in standby (it needs to spin up before it can be used)


None of this really matters to solid state disks as they are pure electronical devices with no mechanics. Their power use is directly proportional to disk activity. While they often do have extra low power modes, you won’t actually benefit much from it since it is not much less than its normal power regulation.

The reason this is plural is because it can also apply to external disks, and desktop macs used to have space for up to six harddisks. The 2009 Mac Pro has 4, for example.