title: Expired queries and appengine
body: <p>Within a task, I'm iterating over a collection of items with a query. After each entity is fetched from the query, I am also performing a URL request. After iterating over a large number of these items, I'm seeing the following error:</p>
  
  <pre><code>BadRequestError: The requested query has expired. Please restart it with the last cursor to read more results.
  </code></pre>
  
  <p>What is the lease on a query once you create it? </p>