I was looking for a way to enable https for a limited number of users who are normally on a whitelist. To use Let’s Encrypt, I have learned so far that port 80 needs to be open for any IPs. I already found many posts where people have been told that they cannot limit that number of IPs, so I am not going to ask that again.
In those posts, hover, my question was not answered, or at least I did not find it: is it possible to limit the time the port is open?
My idea would be: close all unnecessary services, open port 80, get certificate, close port 80 (except for the systems on the whitelist), restart all stuff. ~80 days later, repeat for renewal - and so on. Is this possible? If it is possible, are there important things I have to consider while doing it?