def get_epoch_namespace_receive_fees_period( block_height, namespace_id ):
    """
    how long can a namespace receive register/renewal fees?
    """
    epoch_config = get_epoch_config( block_height )
    if epoch_config['namespaces'].has_key(namespace_id):
        return epoch_config['namespaces'][namespace_id]['NAMESPACE_RECEIVE_FEES_PERIOD']
    else:
        return epoch_config['namespaces']['*']['NAMESPACE_RECEIVE_FEES_PERIOD']