I'd love to see BackBlaze offer the option to select "mission critical" folders that have super-long-life (Time Machine-like) version retention. Give everyone a few gigabytes of this for free, charge a premium to increase that space.
The point of making it a UI is, first and foremost, to get people thinking about this question. And it gives people the option to acheive what you just described without stumbling upon a post like yours on Hacker News.
Something like Attic, Borg, CrashPlan, Restic, etc, that allow snapshot retention periods, like "1 per year for the last X years, 1 per month for the last X months, one per day for the last X days".
> I completely agree that something like RAID is not backup, but 30-60 days seems comparable to other backup services and covers most scenarios.
That doesn't protect against bitrot. e.g.
1. File is backed up (snapshot A).
2. File is slightly corrupted by bitrot, cosmic ray, etc.
3. File is modified by user, corruption is unnoticed.
4. File is backed up again (snapshot B).
5. "Backup" service deletes snapshot A.
6. User discovers corruption.
7. User looks to restore earlier versions until an uncorrupted one is found.
8. User discovers that all available snapshots were made after corruption happened.
Or replace "file" with "directory" and "bitrot" with "accidental file deletion" and the user still suffers from data loss.
Mirrors are not backups, and a few revolving snapshot slots is effectively a mirror.
The only consumer-facing system I've used with multi-year retention is Time Machine. Every few years it has trouble "verifying" the backup and I have to start over (it also deletes old backups when you run out of space). Right now my backup only goes to August.