It's good that you've been thinking about your data as something that is valuable to you and needs to be properly backed up. Most people, unfortunately, don't have that foresight.
I can also appreciate that you have this information mirrored on what appears to be 7 different locations.
That said, I'm not exactly sure what you're referring to by "mirroring". Does that mean that you're using a copy mechanism (like rsync) to make an exact copy of the data?
If so, there are mechanisms that could improve your data integrity with fewer devices.
1) Mirroring isn't an optimal strategy for minimizing data loss. Best would be incremental backups, as this can be rolled back to what it looked like in prior dates. So this provides protection against corruption, viruses, and accidental deletion. If using true mirroring, then any of those get sent straight to your backup destinations, and therefore they can't help you get out of it. Most modern OS's have good solutions for this (like Time Machine for Mac and Windows Backup for Windows), and it only requires one connected hard drive (or hard drive array).
2) You need an off-site storage mechanism to be able to recover from something like a house fire or theft. You can have multiple backups but if they're all located at the same spot, then they are all vulnerable to this. I know you're concerned about privacy with cloud-based solutions (and rightfully so), but some offer the ability to use your own encryption keys to encrypt the data located on the cloud storage. That provides good protection against prying eyes. I use Backblaze B2 cloud storage (and have several terabytes backed up there) and use my own encryption keys and backup tools, but there are other options as well. Keep in mind that many cloud backup sites can also seed the information with you sending them a hard drive full of the information, which makes it easier to start a multi-terabyte backup.
3) If you're absolutely against the cloud backup (which I feel represents the most reliable protection against fires, severe weather, etc), then have backup devices that you rotate to an offsite location. I have two backup drives that alternate being located in my drive array and my office at work. So if I have a house fire, I can recover most of my data with the offsite hard drive, and can get the rest from the cloud backup. You mention an "off site archive", so you might already be doing this.(Backblaze would also send me a drive array if needed, but I think that it's a $500 upcharge -- but that is a low price to pay considering how much that data is worth to me.)
Ultimately, I think that you can reduce the number of locations where you store that data and just be smarter about how it's stored, what software you're using to do it, and where it is stored. The simpler (and more automated) you can make it, the better. And don't discount cloud-based solutions, as they offer a number of advantages, the least of which is now having to purchase new drives.
Michael