title: Do I have to unsubscribe from ActivatedRoute (e.g. params) observables?
body: <p>I find many examples where <code>ActivatedRoute</code> Observables like <code>params</code> or <code>url</code> are subscribed but not unsubscribed.</p>
  
  <pre><code>constructor(private route: ActivatedRoute) {}
  
  ngOnInit() {
    this.route.params
      // (+) converts string 'id' to a number
      .switchMap((params: Params) =&gt; this.service.getHero(+params['id']))
      .subscribe((hero: Hero) =&gt; this.hero = hero);
  }
  </code></pre>
  
  <ul>
  <li>Are the route objects and subscriptions destroyed automagically and newly created for every component creation?</li>
  <li>Do I have to care about unsubscribing from those <code>Observable</code>s?</li>
  <li>If not, can you explain what happens with the tree of ActivatedRoute objects in <code>Router</code>.<code>routerState</code>?</li>
  </ul>