In Backblaze's preferences you can click a link 'How long will my first backup take?' - this takes you to a webpage which attempts to estimate how long your backup will take. Each time I go there it says something like 'Freak Out... your data will be backed up in 300 days'. As far as I can tell, this is a false estimate that assumes you haven't made various changes in Backblaze's 'Performance' panel (i.e. switched off Automatic Throttle, and turned on Threading).