That's an approach that makes sense in theory, but in practice you're almost certainly better off assuming a long time horizon for protecting everything. For o

That's an approach that makes sense in theory, but in practice you're almost certainly better off assuming a long time horizon for protecting everything. For one thing, it's not always obvious what's short term vs long term information and you could end up applying short term protection to information that has long term value in a scenario you didn't consider. For example, encrypted session information that expires might not be useful in gaining access to an account, but it could potentially be used to track you in historical data. The other problem is that most systems (and people) aren't great at segregating information that needs short term vs long term protection, so it's hard in practice to have a strategy based on applying different cryptographic protection to different information. Most encrypted protocols and systems deal with a mix of information that ranges from inconsequential if revealed even now to requiring long term confidentiality because it's much harder to try to deal with that information separately. There's also the practical argument that once I have a protocol or system to protect high value, long term info, why wouldn't I just use that for everything? Modern HTTPS is ridiculous overkill for the vast majority of things it protects, but there's really no reason to use something worse even if you could get away with doing so. This is basically the premise of HTTPS everywhere and similar encrypt all the things concepts. It makes a lot more sense to just protect everything instead of trying to figure out what needs protection and what doesn't and hoping you didn't get it wrong or that nothing changes over the years. Same goes for post-quantum crypto. You might be OK not adopting it for things you think don't need protection beyond the time a practical quantum computer comes around (good luck guessing that time horizon btw), but it's both easier and less error prone to just post quantum all the things.