You could clear your controller properties in the route deactivate hook: is executed when the router completely exits this route.
App.FormController = Em.Controller.extend({
clearForm: function() {
this.setProperties({
name: null,
age: 0,
....
});
}
});
App.FormRoute = Em.Route.extend({
deactivate: function() {
this.controller.clearForm();
}
});