I played with my settings and mine went faster. The times I was not on the computer I maxed out my backup speed and lowered my internet speed. Then I did opposite when I needed to be on the internet. I think it took me 10-12 days total. It said a crazy amount at the beginning though. I don't remember that number. I just remember being happy that it was under two weeks.
Something else I did to give me peace of mind before I started doing my online backup was doing a back up on a separate EHD. Then I knew I had all the information so it really didn't matter how long it took. I wanted to have it on an EHD anyway to store in our safe deposit box so this worked for me.
Also.....I did a full back up from backblaze and it was AWESOME!!! I was switching computers and had to get all my info on my new computer. It worked like a charm and was very fast!