I have 5 20TB HDDs in a RAID array at home, in the real world I get a little over 72 of them. I can lose one disk and have no data loss, though
As for how quickly you fill it up, I’d say that really depends on how much data is redundant and how many backups you want to keep.
Forget about EA, they’re a different company. Ubisoft is the one you want to worry about, they own Watch_Dogs and all related copyrights like DedSec