title: When does (void)dealloc get called in an AppDelegate?
body: <p>I understand that instance variables are released in <code>dealloc</code> (as shown below), but when exactly is it called? Are all instance variables released upon app close, or is there an accepted way for them to be deallocated individually as they become unneeded?</p>
  
  <pre><code>- (void)dealloc {
      [fred release];
      [wilma release];
      [barney release];
      [betty release];
      [super dealloc];
  }
  </code></pre>