[red_admiral]

The NSA has a copy of your ciphertexts on their disks today. What could stop them from trying to decrypt it in 5 years' time? It's not like they will be held back by any Terms & Conditions.

The only way you can do any "not after X time" decryption even for honest-ish users is if the decryption involves getting extra key material from some server that erases it or shuts down at some point. But even that doesn't help if someone can break the crypto.

[dogsledsleddog]

I don't think that is true, current PFS algorithms are probably all just an inconvenience PQ, but I think they suggest strategies where one has to have a key at the time of a negotiation or even be part of a decision in a negotiation to ever have the session key as long as the parties discard it.