Let’s Encrypt will be reducing the validity period of the certificates we issue. We currently issue certificates valid for 90 days, which will be cut in half to 45 days by 2028.
This change is being made along with the rest of the industry, as required by the CA/Browser Forum Baseline Requirements, which set the technical requirements that we must follow. All publicly-trusted Certificate Authorities like Let’s Encrypt will be making similar changes. Reducing how long certificates are valid for helps improve the security of the internet, by limiting the scope of compromise, and making certificate revocation technologies more efficient.
It really just helps in cases where you get hacked, but the hacker doesn’t have continued access. Say someone physically penetrates into your building, grabs the key through an unlocked station, and leaves.
That being said, like you mentioned, if someone is going through this effort, 45 days vs 90 days likely won’t matter. They’ll probably have the data they need after a week anyways.
Encryption key theft really requires a secondary attack afterwards to get the encrypted data by getting into the middle and either decrypting or redirecting traffic. It’s very much a state level/high-corporate attack, not some random group trying to make a few bucks.