Chained cp not firing

gistfile1.js

import Ember from 'ember';
import DS from 'ember-data';

// results is never updated apart from for the initial reference (from a template)
export default DS.Model.extend({
  isNotSaving: Ember.computed.not('isSaving'),
  isNotDirty: Ember.computed.not('isDirty'),
  isSaved: Ember.computed.and('isNotSaving', 'isNotDirty'),
  results: Ember.computed('isSaved', function() {
    return ...;
  })
});
// Works but fires too often if I don't check the parameters and I need to cache results incase I want the results to remain the same
export default DS.Model.extend({
  results: Ember.computed('isDirty', 'isSaving', function() {
    return ...;
  })
});