Built based on; http://stackoverflow.com/questions/19245918/how-to-propagate-backbone-stoplistening-to-prevent-memory-leaks

backboneExtenions.js

define(
    [ 'lib/underscore', 'lib/backbone' ],
    function(_, Backbone) {
        "use strict";

        /**
         * An extension of the Backbone `off` method.
         *
         * This method will trigger <code>onNoObservers</code> when
         * there are no more observers left.
         */
        function extendedOffMethod() {
            Backbone.Events.off.apply(this, arguments);

            //No events or no keys.
            if (   (!this._events || _.isEmpty(this._events))
                && typeof(this.onNoObservers) === 'function'
            ) {
                this.onNoObservers();
            }
        }

        /**
         * Callback for calling stopListening methods
         */
        function autoCloseCallback() {
            this.stopListening();
        }

        var module = {
            /**
             * Adds Events API extensions.
             *
             * Methods Added;
             *   <code>onNoObservers()</code>
             *
             * @param {Backbone.Events} eventsObj The events object to extend
             */
            extendEventsAPI: function(eventsObj) {
                eventsObj.off = extendedOffMethod;
            },

            /**
             * Automatically close an object when nothing listens to it anymore.
             *
             * @param {Backbone.Events} eventsObj The events object to auto stop listening on
             */
            autoCleanup: function(eventsObj) {
                module.extendEventsAPI(eventsObj);
                eventsObj.onNoObservers = autoCloseCallback;
            }
        };

        return module;
    }
)