Divide your crypto key into 3 pieces. You own the third; Two other trusted third parties have the other half.
Every time you open the encrypted vault, you enter a key, and send your password to one of the trusted third parties who.submits their half of the key.
Your trusted third parties have an agreement that you contact them every N days, otherwise, they will automatically perform a secure destruction of their half of the key Upon inactivity, or upon your request, they will destroy the key, and forward your request to the other TTP.
Your communications with trusted third parties are conducted over a secure channel, each of you has a Public-Private keypair stored on tamper-resistant SmartCards.
Your trusted third parties' half of the key is stored on a tamper-resistant blackbox, and they don't have access to the key itself: only an encrypted message which Your smartcard is required to decrypt.
You might choose to use anonymous third-parties. Requests to open your vault are published to Bitcoin public blockchain.
The response contains an encrypted secret key, and the decryption key is held by you only in RAM per decryption.
If there is no request to open the vault for N days, then the keys are automatically destroyed by the 3rd parties, and you pick N.
For some data, N might be 5 days.