Those who are running long term investment, always have to undergo the active maintenance of seed phase, password, device for instance if your phone lost, you have to look for a way to restored everything into your new device, most people lost their seed phase, private keys and wallets that's why I have come up with little ideas especially if you're this carefree person.
Let me ask you, is their anyway a seed phase can be maintained? I don't know if you can explain more about seed phrase maintenance, if you have created a wallet and you have property secured your private key, I don't really know maybe their is any other cost of maintaining your private key.
Once you own bitcoin wallet or other crypto currency, thinking of how long you can maintain your wallet follows this steps,
First send your seed phase or private keys to your emails, also use them to compose a little song only can listen anytime, write it down in your diaries, and makes sure have a google doc to save your wallet keys and other information.
I think you didn't read properly about wallet security before writing this post, If you have proper understanding about wallet security, then you will know that securing your private key on email address is really a bad idea, if you are securing your private key, make sure it's stored in a place where their is no internet connection, if your private key is stored in your email address, then your email address can be compromised and your private key will be exposed.
Securing your private key in your diaries is not a bad idea, but your diaries can easily be distroyed incase if their is fire accident or water accident, the best method I think you can use to secure your private key is by carving it on iron steel, it will be secured incase if their is fire or water accident.