What max-age to specify in the HSTS parameters?

Question

Apache HTTP Server

Hello.
I want to implement HTTP Strict Transport Security. There is https and a certificate from let'sencrypt for 3 months.
What max-age to specify in the HSTS parameters?
Do I understand correctly that if the certificate expires, then I will not be able to access the site?
Now there is a redirect from http to https (RewriteEngine On).

Answer 1

What max-age to specify in the HSTS parameters?

The largest possible.

Do I understand correctly that if the certificate expires, then I will not be able to access the site?

This is for the best for most sites.
But if you don’t want the certificate to end, then don’t copy it or create it manually, but automate this action and set up monitoring.