A backup is useful only if it can be found, read, and used correctly under stress. Test the recovery process with a small or empty wallet before relying on it.
Document wallet type, required devices, passphrase use, and the sequence a trusted person should follow. Do not place the full seed phrase in a normal will or unencrypted cloud document.
Review the plan when devices, wallets, locations, relationships, or laws change. Complex multisig or inheritance systems should be tested and may require qualified legal advice.