code: function purgeJunkUnhandledJoints(){
  	if (bCatchingUp || Date.now() - coming_online_time < 3600*1000 || wss.clients.length === 0 && arrOutboundPeers.length === 0)
  		return;
  	joint_storage.purgeOldUnhandledJoints();
  }
docs: We may receive a reference to a nonexisting unit in parents. We are not going to keep the referencing joint forever.