title: Does firebase3 storage url changes with time or location
body: <p>I was wondering if I can save the url that I get from storage in to my database and retrieve the link every time I want the image? Right now, I am calling the following function each time I need to get an image and it is slow. I am just afraid that the link might change depending on where the user is and time?</p>
  
  <pre><code>           storage.ref(thisEvent.eventImgInReference).getDownloadURL().then(function (url) {                         
                              //here I just add the image url
                              thisEvent.eventImgLink=url;
                              //
                              $scope.$apply();
                          }).catch(function (error) {
             });
  </code></pre>