perhaps if you do a 2 of 2 or something. However, if you have a threshold wallet (eg 2 of 3) I don't agree that it's twice as likely to lose a part.

The issue with multiple copies of a single key is that you are much more exposed to theft, and if theft happens, you won't even know which key was compromised. So if you stored one with a friend, one with your lawyer, and one in your own home and your bitcoin gets stolen, you now get to deal with the consequences of doubt and suspicion across all your relationships. Much better a 1 of 3 multisig where you would at least know which key did the signing.

Password only in your head is pretty risky, too, in my mind. If you are willing to take the risk that you forgetting something will lose all your bitcoin, then go for it. But in that case, why not just have one key and hide it well? or for that matter, just memorize your seed phrase and leave it at that? But if you hit your head, it's gone.

I'm interested in a solution that doesn't make me the single source of failure.