Loosen the requirements check for TTL below one month

This checks values (24h, one month, one year) seem very strange if not dangerous.

$this->config->get('cache.page.max_age') is the value that Drupal use as max-age in the cache-control header of the response send to the client.
This value will be used by reverse proxy such as Varnish but also by the client browser which could not be purged by Drupal.

Could someone explain these choices?
Do you rely on conditional request header (If-None-Match, ...)?

See also "Cache Max Age warning text"