title: boto3 s3 generate_presigned_url ExpiresIn doesn't work as expected
body: <p>I have tried to generate <code>pre-signed URL</code> with 7dsys expiration time.
  (It is saying maximum duration is 7days, <a href="https://stackoverflow.com/questions/24014306/aws-s3-pre-signed-url-without-expiry-date">AWS S3 pre signed URL without Expiry date</a>)</p>
  
  <pre><code># It is called and retruned in AWS Lambda
  boto3.client('s3').generate_presigned_url(
      'get_object',
      Params={'Bucket': bucket, 'Key': object_key},
      ExpiresIn=(60*60*24*7)  # 7days
  )
  </code></pre>
  
  <p>However, it seems not to retain the <code>pre-signed URL</code> for 7days but just several hours. The <code>pre-signed URL</code> just returns the XML format after that.</p>
  
  <pre><code>&lt;Error&gt;
    &lt;Code&gt;ExpiredToken&lt;/Code&gt;
      &lt;Message&gt;The provided token has expired.&lt;/Message&gt;
  .
  .
  .
  &lt;/Error&gt;
  </code></pre>
  
  <p>It seems even to be different expiration time every time I try, sometimes 5 hours, sometime 12hours.</p>
  
  <p>I don't know why.</p>