Not OP, but you seem to be thinking about this in a particular way. There are some things I don't want to be read, but not in the sense that they're "high value" in a way that would attract motivated attackers. I'm not worried that my friends and family are going to shoulder surf, trick me, hack my devices, or threaten me with a big wrench to get at my private thoughts.

For these purposes, written journals or letters can be opened opportunistically if found. If I had a safe, it would be opened after my death. If the documents are known to exist in the clear anywhere, then they're subject to probate.

But if they're encrypted and the secret is unknown and hard to guess, then most likely everyone gives up and that's the end of that.