title: When should $destroy be called on scope?
body: <p>I'm aware that $destroy should be used to avoid memory leaks, but it's not clear what is precise and definitive list of cases when such leaks can occur.</p>
  
  <p>When exactly should one call $destory on scope?</p>
  
  <p>This question is not about does or not $destroy removes event listeners. It is question for list of cases when one should deliberately call of $destroy() method. Also this question is not about $on('$destroy').</p>