protected function getLastValidItem()
    {
        $validItems = $this->getValidItems();
        $result = null;
        if( !empty( $validItems ) )
        {
            $result = null;
            $lastTime = 0;
            foreach($validItems as $item)
            {
                if( $item -> attribute( 'ts_visible' ) >= $lastTime)
                {
                    $lastTime = $item -> attribute( 'ts_visible' );
                    $result = $item;
                }
            }
        }
        return $result;
    }