title: Validate propTypes on parent and child components?
body: <p>Should I be adding propTypes to parent components and their child components?</p>
  
  <p>For example I have a <code>&lt;Header modal={this.state.modal} lives={this.state.lives} score={this.state.score} /&gt;</code> component that is passed 3 props and I validate like so:</p>
  
  <pre><code>const Header = function(props) {
    if (props.modal) {
      return (&lt;Logo logo={logo} /&gt;);
    } else {
      return (
        &lt;div&gt;
          &lt;Lives lives={props.lives} /&gt;
          &lt;Score score={props.score} /&gt;
        &lt;/div&gt;
        );
    }
  };
  Header.propTypes = {
    modal: React.PropTypes.bool.isRequired,
    lives: React.PropTypes.number.isRequired,
    score: React.PropTypes.number.isRequired,
  };
  </code></pre>
  
  <p>As you can see there are two child components <code>&lt;Lives lives={props.lives} /&gt;</code> and <code>&lt;Score score={props.score} /&gt;</code>.  I've added propTypes to those components as well.  </p>
  
  <pre><code>const Score = function(props) {
    return (
      &lt;p className="score score--right"&gt;
        {props.score} pts
      &lt;/p&gt;
      );
  };
  Score.propTypes = {
    score: React.PropTypes.number.isRequired,
  };
  </code></pre>
  
  <p>So is it redundant to be checking the same props twice?  And is this just overcomplicating things (making my code more difficult to manage).</p>