I use Ubuntu 14.04's built-in Backup utility (backed by deja dup) and use daily backups. Every so often (every couple of months) Backup insists that it create a "fresh backup" in case of "backup corruption". I imagine that the motivation for doing this is that if the backup files themselves are on some media which may suffer bit rot from cosmic rays, current spikes, etc or aren't redundant (almost all media is like this for the average computer user), having new fresh backups from time to time would be nice.
However, there are users, such as myself, who use backup media which are much less likely to suffer from backup corruption, and don't need regular fresh backups. In my case, my backup media is a ZFS RAIDZ filesystem whose redundancy and bit-level checksumming prevents random data corruption. Additionally, creating fresh backups takes up large amounts of space (close to 1TB) and so in my case I'd rather just use the incremental backups ad-infinitum as Time Machine for the Mac does.
Is there a way, in Ubuntu 14.04 Trusty, to turn off the "fresh backup" functionality entirely? Another askubuntu.com answer hints at a "secret config key" but doesn't disclose where it is.