code: public function purge( $days_older_than = 60, \wpdb $wpdb ) {
  
  		$days_older_than = absint( $days_older_than );
  
  		$tn = $this->table->get_table_name( $wpdb );
  
  		$sql = "DELETE FROM {$tn} WHERE time < DATE_SUB(NOW(), INTERVAL $days_older_than DAY)";
  
  		$wpdb->query( $sql );
  	}
docs: Purge all records older than 'n' days.
  
  @since 1.0
  
  @param int   $days_older_than
  @param \wpdb $wpdb