protected function getExpirationTimestamp($lifetimeInSeconds = false)
    {
        if ($lifetimeInSeconds === false) {
            $lifetimeInSeconds = $this->lifetime;
        }
        if ($lifetimeInSeconds === self::IMMORTAL_LIFETIME) {
            return false;
        } else {
            return date(self::MYSQL_TIMESTAMP, time() + $lifetimeInSeconds);
        }
    }