When I saw the title of this thread, I was expecting something completely different because it indicated the cost of keeping your wallet, which I was curious about because I don't spend any money to maintain my wallet.
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.
Other forum members have discussed how dangerous it is to preserve your private key or seed phrase online, therefore keeping it in your email is not recommended. Furthermore, writing them on paper is a temporary solution because papers can shred and be washed or burned out in the event of an accident or an unanticipated natural disaster.
In this post created by @fillippone, you can learn
How to Secure Your Seed Phrase. It will provide you with a permanent answer to seed phrase troubles.