title: The right time to destroy an interstitial ad
body: <p>When is it the right time to destroy an interstitial ad in Google Mobile Ads Unity Plugin?</p>
  
  <p>The docs say:"It is important to explicitly destroy the interstitial <strong>before letting it go out of scope</strong> so that it can be properly released by the plugin."</p>
  
  <p>Should the interstitial ad be destroyed right after it shows? when it is clicked? or when about to be closed?</p>
  
  <p>Any thoughts? Thanks.</p>