If a BI computer or NAS is stolen, all recordings can be lost. Cloud backup is a potential solution, but it needs to be (nearly) real-time to catch the thieves. I have found that sync (from a variety of sources) cannot keep up with multi-TB-sized folders (stay within 5 minutes current) and may have technical problems with growing files.
If you have a need for near-real-time cloud capture, I think I have a solution. It works for me. iDrive has both Cloud Backup and Cloud Drive. I use Cloud Drive for sync of New (small GB folder, e.g., 2GB). BI is set to move New to Stored and Stored is backuped up using Cloud Backup. As a result, Sync/New in the cloud is current to within less than 30 seconds and available to view in the event of theft, and I have longer-term backup in Stored/Cloud.
NOTE: to keep stored backup current, I have it set to verify every hour, so it never gets too far behind, and to delete files deleted from Stored. Your times and folder sizes can be adjusted to your needs.
Because iDrive keeps deleted files in Trash for 30 days, I keep Stored sized for 1 – 2 weeks on local SSD (and use Auto Archive in iDrive to clear cloud storage).
I use this for home security and expect 30 days to be an adequate history. If you use recording for business and need longer retention times, physical security for your BI system and NAS probably is needed but would be overkill for a home.