I do a monthly offsite backup. I use rdiff-backup for plain text and 7z with encryption for data I want to keep private, but I am on the lookout for more efficient solutions. I looked at bup, but two things stop me from using it: no encryption, and inability to delete old backups to reclaim space. To me, attic (https://attic-backup.org/) looks attractive so this is what I am going to try soon.