[mikekchar]

Why does it need to be scanned years later? I suppose if you are mitigating the risk of going to prison or something like that, then it might make sense.

But either way, you can print to paper and store it in a fireproof safe (or probably better still -- a safety deposit box). There are lots of methods for ensuring printed paper survives for a long time -- if you google it, I'm sure you'll find more than you want to know.

My personal method is storing passphrase encrypted on multiple USB drives (they're cheap) and replacing them every year or so (they're cheap).

I think a more interesting question is: how do I provide access to my non-technical wife in case I am incapacitated or dead? Especially, how do I convince her not to put the passphrase on a sticky note on the fridge?

[edibleEnergy]

It'd be scanned years later if the USB drive I've backed it up on for regular infrequent use goes kaput on me ;)

The replacing every year or so sounds like the most robust way to do it with current best practices but that requires a lot of maintenance.

[bhhaskin]

Encryption. If you encrypt files with the public key you are going to want to keep private key around long after the signature key is expired. The alternative is to decrypt and re-encrypt your files when you rotate keys out, but there is always a worry of forgetting something.