CLTV == CheckLockTimeVerify

Let's you lock a script until a certain amount of time/blocks has passed. You'd build a script with OP_IF around that, with a primary multisig branch that can spend the coins with n-of-m sigs, and a second branch that unlocks after some time that invalidates the first branch and let's you spend from a singlesig script which would be your long term backup key.

You can use convoluted key/paper backup distributions for the primary branch with the knowledge that if you mess up you can spend your coins from the backup key in the future. Since there's no risk of blackholing your coins if you lose too many of the multisig keys, you can go afford to risk destroying them.

It has the same basic design as what you are proposing: stringent security requirements at first, lose backup sometimes in the future.