I have also had the problem of Wipe Free Space not finishing after begin given 12h to run. But, I understand that wipe free space only writes random data over memory that has already been freed-up by deleting files. In other words, wipe free space prevents more advanced software from recovering deleted files.
I think Augeas has missed the point, which is that the feature does not terminate properly: Wipe Free Space gets stuck at ~97%, and one must press 'Cancel' to end it. After which, I am not sure that Wipe Free Space has done its job properly and what it has left lying around.