The whole point of offline storage is to guard against the risk of whatever internet-connected device you use to store your keys getting compromised.

If you make a mistake or fall victim to an attack that lets someone steal the encrypted file containing your key, there's a good chance the attacker will also be able to install a keylogger and get your passphrase.

The way I do it, is have a bootable usb stick with a clean install of Tails OS that has all my crypto stuff. I also have a gpg encrypted seed file on my google drive as a backup with MFA turned on.

I don't think offline storage is necessary as long as you're certain your system is clean, which a clean linux install helps.

If he can run a keylogger on whatever computer you use to unlock your wallet, then it does it really matter whether you store it offline on USB stick in a safe or not.

That's where hardware wallets like Trezor or KeepKey come into play. Any transactions are signed on the device and sent back to the computer; your private keys never leave the device.

A bitcoin 'wallet' is a strong encrypted key. The question is where do you keep that key.

But where do you store the key?

In my head? The same place I store the passphrase to my password manager.

With no backup? What if you suffer a massive head trauma (or an unfortunate death), no way to recover your millions of dollars for friends and relatives? I'm guessing people put this stuff in their wills these days, how secure is a will?

I have an encrypted file with online banking passwords, account numbers, etc for my wife.

It's on a USB stick in our fire safe, and also in our safe deposit box along with a passphrase hint that my wife or daughter would understand, but is not obvious to an outsider.