title: Destructor not being called for XAML pages
body: <p>I am creating a Windows Phone (8) App. I have 2 XAML pages. If I manually test the following:</p>
  
  <pre><code>1. From 1st page, go to 2nd page
  2. Press the physical Back button.
  3. Go to #1.
  </code></pre>
  
  <p>Eventually (afte switching back and forth ~15 times), the app runs out of memory and crashes. I put debug statements in Page 1's and Page 2's destructors, but it appears that they are never being called.</p>
  
  <p><strong>How can I ensure that this problem does not happen?</strong></p>