title: Does firebase ever recycle tokens?
body: <p>I have an app which is receiving a token from firebase.  From what I understand, the next step would be to assign that token to a user in my database, perhaps in a "lastFirebaseToken" column.  Then I could call the firebase api using this token to send messages to a specific device.  If any of this is wrong, my question won't make sense, but assuming all of the above:</p>
  
  <p><strong>Would there ever be point at which a token that was assigned to a device in the past gets re-assigned to a different device?</strong></p>
  
  <p>In any case, I'll probably make the <code>lastFirebaseToken</code> column UNIQUE, but I still find this question important to my fundamental understanding of firebase.</p>