I think I am more concerned about my close ones reading them.
The "look over your shoulder" attack is omni-present. (Also easier to prevent with paper, in general, than with a larger computer screen.)
A simple safe will stop most prying people. And if you die... Well, you are dead... there ain't much stopping anyone at that point.
Keeping secrets is hard. Very hard. There's a reason for the most part... I don't bother, except if/when I need to, and even then, if they can be timed out, all the better.
Paper also has a big benefit in that we know how to destroy it. :)
... Simple things are often best. Understanding how your system will bend/break is critical in security situations.
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.
In the end, a computer may be a bit safer. But if it is high enough value... someone will find a way.