title: Taking an iAd across multiple screens
body: <p>I'm sure there's a simple answer to this but it's beginning to annoy me now!</p>
  
  <p>I have an iAd integrated into my app which appears and works on the screen I've implemented it in. The app uses a NavigationController to move between multiple screens, but the iAd is only on one of them. After moving from start to finish through my app several times I get a message appear in GDB saying:</p>
  
  <p><code>Too many active banners (11). Creation of new banners will be throttled.</code></p>
  
  <p>The app then crashes.</p>
  
  <p>I have tried looking through the Apple documentation and searched on Google and can't see a solution to the problem.</p>
  
  <p>If anyone has any idea how I can resolve the issue it would definitely stop me from going mad! Thanks.</p>