Personally I store all “Very important data” on it - things I really don’t want to loose even if my data storage at home and my cloud storage gets compromised. Among them:

• Photos of life events. Wedding, photos of the kids, photos of relatives that are now deceased, etc.

• Important documents. Birth certificates, copies of IDs, passports, insurance documents, degrees and certificates, banking/taxation/accounting documents, bills for the important stuff like major renovations, the expensive IT stuff, etc.*

• Backup of important files (for me Uni files for my lectures, some work files, backup of the password DBs, plans for the house, a tutorial how to receive files from the cloud storage, decryption keys, etc.)

(*: This is more a theoretical choice - as I can get 100GB media for the same price as the 50GB I currently simply copy the full paperless file storage. But the script normally only copies these. They are flagged with a custom field in paperless)

I do not use addition to the storage,so no “these files are new since the last copy” but I simply make a full backup of these files every time (usually three times a year). This reduces the risk of one backup being compromised - very likely I only fall back 4 month which is tolerable. The discs itself are stored in a locked box in a bank vault a bit further away. I have to go there a few times a year anyway,so it’s not hassle. (And they have great coffee). The box costs me 50€ a year and has enough room for 50 years of M Disks and a few extra items.

Anything taxation related must be stored for 10 years even by private individuals here,so there is that.

My customers (smaller health care organisations, e.g. your fellow neighbourhood dentist or GP) usually store patient data and accounting data on them. They need to store them long term (up to 30 years) for legal reasons, additionally they don’t want a opposing lawyer to later tell them “you have manipulated the data”. Having multiple copies that cannot be manipulated reduces that claim to “you manipulated before you stored it” and we have other ways to fight that.