I do full disk image backups of my half full 1TB OS drive to a HDD every day, and upload archive to remote storage every few nights, so about 1-2 TB a week of uploads. Then i have my other HDDs backed up once a week, so about 10-20gb of changes a month.

Now i started doing photography as a hobby, and boy, are those raw files large. 24mb each. Last weekend i was on a short trip with friends, 75 GB of raw photos and videos. Gotta back those up, the faster the better.