[tyfon]

In Norway you need to keep accounting data for ten years to be compliant with accounting laws so I you lose eight of them you would be in violation.

Edit: I see you mean retention, I guess if you discover after a year that your backup routine is malfunctioning and you need older backups but that is not that common I'd guess.

[moviuro]

backups and archive are a different matter. Archives are meant to not be altered; ever (WORM disks[0]). Backups are made to be rewritten, ~~lost~~, or used for restoration.

[0] https://en.wikipedia.org/wiki/Write_once_read_many