Backblaze has a policy of allowing backups of external disks, but the disks have to be connected at least once every 30 days, or they'll delete the backups. I understand they want to avoid abuse, but the lack of any grace period, or ability of support to ad an override, really soured the service for me.

Huh, I had to start paying them $2 more for my nonexistent PC I think, but otherwise was fine. I have only 1 TB of total storage on that PC though, so maybe that’s the reason.

You can just pay extra for extended or infinite retention. https://www.backblaze.com/cloud-backup/features/extended-ver...

I did this, it's come in use a few times..