Concurrent refinement threads explicitly compare the current number of buffers with their deactivation threadhold to determine whether to deactivate. They also call apply_closure_to_completed_buffer with a "stop_at" of the green zone value, and deactivate if it returns false. It would be simpler to skip the explicit check for deactivation and just call apply_closure_to_completed_buffer with the deactivation threshold as the stop_at value.