title: How much time usually an iOS application takes to get suspended from the background state?
body: <p>I need my iOS application to work continuously on the background mode but seems it gets suspended after a while. I've 2 questions here:</p>
  <ol>
  <li>Is there any definite time for the application to get suspended from the background?</li>
  <li>Is there any way I can get the specific time of this suspension process?</li>
  </ol>