The amount of local disk space used by backups can be quite large on some websites, there is definitely more value in keeping a longer history on remote storage rather than local storage. An extension of the retention rules allowing you to keep a longer history of backups on local storage would add a lot of value to the premium plugin.
For example:
Local storage – Weekly files backup – keep 1 week only / Daily Database backup – keep 7 days
Remote storage – Weekly files backup – keep 12 weeks / Daily Database backup – keep 84 days (7 weeks)
eping a longer history on remote storage rather than local storage.
This idea was posted in UpdraftPlus - backup/restore plugin and tagged backup, retention, storage on December 21, 2018 by 
francis7.
I would definitely be interested in this add-on as well. This is especially true on old sites, where you want a backup in cold storage, but need to have recent backups on the server in case of an issue.