But revocation is different from expiration. If you're worried about a cert being compromised long after expiration and used to back-date a signature, you can

But revocation is different from expiration. If you're worried about a cert being compromised long after expiration and used to back-date a signature, you can show a warning, add a second signature with a local key at time of installation, use a blockchain to prove age, have a timestamping service generate its own signature at time of generation, etc.