title: obj.ttl in Varnish 4.0
body: <p>Question about obj.ttl in Varnish 4.0 </p>
  
  <p>I have a small varnish problem and hope anyone can help me.
  I am using varnish 4.0 and I want to increase the obj.ttl based on the obj.hits</p>
  
  <pre><code>sub vcl_hit {
    if (obj.hits == 1000) {
      set obj.ttl = 7d;
    }
  }
  
  sub vcl_fetch {
    set beresp.ttl = 20m;
  }
  </code></pre>
  
  <p>Unfortunately, I receive an error.
   Message from VCC-compiler:</p>
  
  <pre><code> Variable 'obj.ttl' is read only.
   At: ('input' Line 46 Pos 21)
  </code></pre>