Minor formatting fix.
Ensure delta_factor is passed through

  - Testing for the rest of the parameter should be added.
More attribute test.

  - Also test the chaining buffers.
Add expiry field for handling the following:

  - Ensure that normal partial progress are tracked.
  - Ensure no "backward" flow of time, so that negative time will not
    reverse progress
  - Any amount of time beyond expiry will immediately begin a cycle.