title: GCM push notification is not received if app was not opened in a long time
body: <p>I have some apps which are using <code>gcm notification</code>. They work fine but there is an issue here: if I don't open one of them for almost a long time (like 2 monthes or more) it will not receive notifications anymore. </p>
  
  <p>Acctually, I experienced this behaviour with stackoverflow app too. 
  Can anyone explain what is the reason and how to avoid it?   </p>