protected function ttlToMemcachedTime($ttl)
    {
        $seconds = $this->ttlToSeconds($ttl);

        if ($seconds <= 0) {
            return isset($seconds) ? false : 0;
        }

        /* 2592000 seconds = 30 days */
        return $seconds <= 2592000 ? $seconds : $this->ttlToTimestamp($ttl);
    }