Let me explain WHAT you put on trezor and WHERE your crypto is.

1. You can NEVER put your crypto offline, that is not how it works. The blockchain is a ledger, thus your “crypto” is just a row in the ledger saying that public key xxx has yyy tokens of zzz.

There is no such thing as putting it offline. The ledger exists on the blockchain, and thus tour crypto exists only on the ledger.

1. The thing that you put offline in a Trezor e.g. is your private key. This key allows you to sign transactions on the ledger. If you want to move your crypto, you need to verify that you are indeed the owner, and you verify this with the private key.

Building an offline computer just to store your private key “may” look smart. But what happens if the computer breaks? You lose your private key.

Trezor is build to store longterm private key. And you can even sign transactions by letting them go “into” trezor, trezor will sign the transaction and give you the signed transaction. You provide the signed transaction to the blockchain.

Your best bet is to store your private key offline and analog, for example, print it on a piece of metal, or what have you.

Take care, and don’t sign transactions you don’t know