Ask HN: What is the best durable storage medium for critical data backup?

I'm evaluating my current backup and security stance for personal use. My biggest concern right now is backing up keys, recovery codes, and my Keepass password file. There are also some documents I'd like to make sure I preserve.

I have copies of these things on multiple devices and I am currently syncing important documents through OneDrive. I don't really like being tied to Microsoft for this.

I am planning on a NAS at home and encrypted backup (likely to Backblaze, but I'm open to other alternatives if y'all have suggestions).

I'd like to also back up critical documents and data offline periodically - something I could keep in an alternative location. Additionally I'd like to be able to give a copy to my next of kin in case of my unfortunate demise. My understanding is that flash drives and hard drives might suffer from bitrot if disconnected for long periods of time.

Should I be considering optical media? Are there any major differences in terms of retention?

Would an old spinning rust hard drive be sufficient?

I expect that this would likely sit unpowered for months to potentially years. I would like to update - would rewritable optical media be as durable as write-only?

Thanks!

I'm also open to any other thoughts on disaster recovery storage.