I do the exact opposite of what the OP wants. I dive into USB Selective Suspend and Power Mangement for USB Hubs, then change the defaults to keep USB devices running
all the time. Some USB devices don't always recover gracefully when they "wake up".
I learned many years ago that hard disks are often more reliable if you don't start and stop them many thousands of times. I have some ex-server "pulls" (WD Gold Enterprise Class) with more than 6 years running time and only 64 stop/starts. It's obvious they were left running for months on end and only powered down for system maintenance.
Contrast this with a portable USB3 drive that's potentially powered down every few minutes. You could easily rack up 64 start/stop events in one day. Electro/mechanical devices have a tendency to fail at startup when power is first applied. 3.5in hard disk motors can pull 2A from the 12V rail for a few hundred milliseconds as the platters spin up. It's probably the time of maximum stress.
At the end of the proverbial day, what you do with your disk drives is entirely up to you. Just make sure you keep at least 3 copies of important files on different media and don't have them all connected to a single computer simultaneously, If Ransomware strikes, they could all get clobbered.
As
@Phillip Corcoran says, a backup drive is safest from calamity when it's unplugged. If you leave a so-called "backup" drive permanently attached to your PC, it's at risk from malware, viruses, ransomware, accidental file deletion, catastrophic PSU failure, even lightning strikes (I've had two strikes which damaged connected equipment). A secure backup is an isolated backup.
I stopped using my large collection of WD Elements and Seagate USB3 Desktop drives 5 years ago. They run far too hot for my liking in their cramped plastic housings with inadequate ventilation slots. More importantly, I think some or most of them are SMR, not CMR, so they're torturously slow when they become fragmented.
This link claims SMR drives are less reliable than CMR drives. Check your USB3 drives and keep your fingers crossed they contain CMR drives.
https://www.downelink.com/smr-vs-cmr-hard-drives-a-complete-comparison-to-inform-your-next-purchase/
"Across matched 4TB drive models they found CMR reliability averaging between 0.5-1% failure rates per year over 5+ years of service. By contrast SMR models displayed rising risk profiles nearing 2% by years 2-3 as mechanical stress added up. Thats 4X more likely to suffer catastrophic data loss outside of warranty coverage windows!"
By their very nature, SMR drives perform more read/write operations when the disks start to fill up and files become fragmented. A CMR drive has a quieter life.
These days I backup to properly cooled CMR hard disk arrays, plus drives in separate PCs and LTO tape. My 11 USB3 drives just sit in a cupboard and only come out once or twice a year, for a quick check.