You don't need to particularly safeguard the credentials to get to your encrypted blob, they can be in a gmail email you sent to your friends and/or family. They can't read the content but they can give you a copy.

How do you remember where your safe deposit box is after four months in hospital recovering from a cerebral trauma?

There's no perfect solution.

Yea, a friend of mine's younger brother suffered a stroke in college, and couldn't remember his laptop password. My understanding is that at least some of the important files were encrypted.