[mrazomor]

I was in a similar discussion some 10y ago. After a few rounds, we concluded that for a really good reliability you could do the following:

- no service is expected to last long enough or to keep your data safe,

- a physical medium is the way to go,

- create 3 backups stored in different location,

- use a different brand for each backup,

- every 10y review the backups: check the data degradation, rebackup on a new medium if the current one is getting phased away, reencode the content if the format is becoming obsolete & hard to open. [IMO, this is the key point]

Getting the old works of a predecessor on a physical medium is a really good feeling (I know how I felt when I'd discover the old notebooks from my father, uncle, etc.). Based on my experience and Internet, CD-R seems to be a good choice if the data volume allows. But it's getting slowly phased away. (fun fact: a few months ago I found the first CD I burnt -- works flawlessly (although, no checksums checked) after 25y)