public function getDownloadExpirationTime()
    {
        $iExpTime = $this->oxfiles__oxdownloadexptime->value;
        //if value is -1, takes global options
        if ($iExpTime < 0) {
            $iExpTime = \OxidEsales\Eshop\Core\Registry::getConfig()->getConfigParam("iDownloadExpirationTime");
        }

        return $iExpTime;
    }