As most users mentioned, if you can't audit the source code/device (when it's open source) or they make the system closed source, you only can trust them.
In case the hardware wallet fail, user shouldn't lose their money if they made backup and they should able to restore it to another wallet since they usually use same standard (BIP 39).
Theoretically you should trust no one, including yourself. Thats why some people use https://en.bitcoin.it/wiki/Paper_wallet and put it in a drawer.
But do you trust your housekeeper? (¬_¬)
There's no problem if you put it in secure places such as Safe and encrypt the private key with passphrase (BIP 38)
In case the hardware wallet fail, user shouldn't lose their money if they made backup and they should able to restore it to another wallet since they usually use same standard (BIP 39).
Theoretically you should trust no one, including yourself. Thats why some people use https://en.bitcoin.it/wiki/Paper_wallet and put it in a drawer.
But do you trust your housekeeper? (¬_¬)
There's no problem if you put it in secure places such as Safe and encrypt the private key with passphrase (BIP 38)
Agree, found a good tutorial on this https://bitcoinpaperwallet.com/bip38-password-encrypted-wallets/
But still, how to remember the passphrase? Write it down and put into another Safe?
I think remember passphrase/password isn't that difficult when there's big money involved and follow some guide to make/remember password easily (each people might comfortable with different guide). But if you want maximum security, you need to make effort. In this case that would be either :
1. Remember the passphrase/password
2. Keep the paper wallet on hidden location
3. Keep the paper wallet on secure location. But this also require you to keep the keys secure or remember the password/PIN if you use safe/digital lock.
Just choose which one is suitable for you.