In addition to the other reasons given, there's a reliability problem in relying on an ever-growing chain of incremental backups: you can only recover your late

In addition to the other reasons given, there's a reliability problem in relying on an ever-growing chain of incremental backups: you can only recover your latest state if every increment in the chain is uncorrupted. I would much rather use an incremental backup that records the diffs in reverse, so that the latest state is stored explicitly, and the earlier versions are recovered through a chain of reverse diffs. Duplicity's security goals make it hard to implement this kind of reverse diff structure.