I'm having a real hard time wrapping my head around how Public Key Infrastructure could co-exist with every public key being a nonce. I'm not confident that it is impossible, but GP's question seems like an interesting theoretical/categorical question more than a hyperbolic "how short can lifetimes go?".
1 hour lifetimes sounds incredibly complicated to orchestrate on a practical level. Do you use a lot of short-lived ephemeral hosts (e.g. a swarm of docker images)? I'm not sure how 1 hour lifetimes wouldn't cause systemwide chaos in what I consider a "typical" microservice architecture.