Borgmatic runs consistency checks [1] once a month on all repositories and archives and I occasionally retrieve older versions for selected files (archives with --verify-data only once a year or whenever I feel the need - there's 9TB of data in the borg repo, which takes a bit to scan). Note though that borg is not my main backup, it is the fallback "3" in the 3-2-1 principle, where my primary data is a ZFS Raidz2 and my primary backup is an offsite ZFS Raidz2 in pull mode. I added borg because I did not want to rely on a single software (ZFS), although this fear was unstained so far.

[1]: https://borgbackup.readthedocs.io/en/stable/usage/check.html