Sorry guys for not being around for long. Thanks for the overwhelming response from all. There are some great suggestions while I guess I may not have explained my scenario in the best way.
LTO is out, because although 95% of my data is not re-used often, I have old clients who come back to me after very long. So I some times need to revisit / re-edit their data. So I cannot catalog or update a serial device as often. Too much time consuming.
Backblaze offers UNLIMITED Personal backup just for $60 / year / per PC. Not B2. I need just archival for my workstation. At 128MBPs broadband the estimate says ~40 days to backup the entire 40 TB. I can wait…Not sure of restore though. Need to ensure periodically that backups are in good health.
NAS – Initial cost is higher with 10 x 4 TB HDD. May need 2 boxes for that many HDD. Will need additional UPS. May need to keep at home during lock downs to ensure all is working fine. Data recovery may be costlier for LINUX file system as against a PC NAS. Works as a cloud server too for teams to collaborate.
PC as NAS – Has all benefits of a boxed NAS, in fact much cheaper. I have the required expertise to set it all up. Just that the foot print is bigger with mice, keyboard, monitor and an UPS for keeping at home. With 24 x 7 powered on will bother others at home.