public function getLifetime() {
        if (!self::$lifetime) {
            $sessionExpirationHours = engineGet('Config', 'sessionExpirationHours', false);
            if (!$sessionExpirationHours)
                $sessionExpirationHours = 2;
            self::$lifetime = 60 * 60 * $sessionExpirationHours;
        }

        return self::$lifetime;
    }