The other point to remember is BB is not for archiving. BB states this itself. At least with external drives it is possible to archive.
A B2 based backup solution costs more but you don’t have those limitations.
[1] https://help.backblaze.com/hc/en-us/articles/217666628-What-...
If you have an externally attached drive on your computer and it isn’t connected in 30 days and your computer is online, they erase that backup of the external drive.
If you reconnect your computer after a month and you don’t have the external drive connected, they erase your backup.