[Inquiry] In which cases do GCM server return 'NotRegistered'?

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Prepare device and receive GCM id using an app that uses GCM.
2. Do nothing for a long time until GCM servers remove GCM id from the server.
3. Try to use GCM using the previously generated GCM id, and the app receives 
'NotRegistered'.

What is the expected output? What do you see instead?
  One of the device received 'NotRegistered'.
  An app in this model is using GCM(Google Cloud Messaging) for inviting his or her friend.
  We found the error message at http://developer.android.com/reference/com/google/android/gcm/server/Constants.html#ERROR_NOT_REGISTERED,
  but could not see any explanation about interval of the invalidation by the server.

Question is:
  a) If the user does not send/receive GCM packet, could you explain how many days Google servers maintain registered GCM ID on the server-side?
  b) In which cases do GCM servers remove GCM registered ID?


What version of the product are you using? On what operating system?
Android JellyBean

Please provide any additional information below.
N/A

Original issue reported on code.google.com by [email protected] on 8 Oct 2013 at 2:33