Getting External Hard Drives to Sleep/Spin-down

Quick run down of my setup before I get to my question.

Boot Drive: 128GB SSD
Media Drive: 2TB internal HDD

1st Backup: 3TB external HDD
2nd Backup: 3TB external HDD

I keep most of my stuff on the external now, really only leaving stuff I regularly listen to /watch on the internal drives. I'm using SyncToy 2.1 to mirror one drive onto the other, I would have liked to triple save it with a third 3TB, but with my budget two will have to do for now. My question is whether or not I can have the external drives stop spinning while plugged in. I know that in the Power Options I can set the hard drive to turn off after a while, but I think that's just for when the whole computer goes to sleep. I've been running Folding at Home continuously for over a month now, and I'd like to keep doing that so sleeping isn't an option for me anymore. But I worry that these external 3TB drives are kind of cheap (I got them each for around 115$ - 120$), so... when not using them I'd like them to just go to sleep. I'm not an expert on this, but I imagine less strain and heat will help them last longer.

I looked in Disk Management but all I'm really seeing here is ways of formatting the drives (which is certainly not what I want to do). I figured I could just unplug them and replug them when needed, but I know that doing that excessively can wear out the ports, which could just as easily kill my ability to use the drives. Any help would be greatly appreciated.