But where do you hodl your alt coins that are not supported ?
That definitely is the best method to be protect your bitcoins and your ethereum. Even if your computer gets hacked your money is still safe, and compared to the potential loss that one can suffer when being hacked, the investment in a hardware wallet is really worth it.
For altcoins that are not supported on the ledger you can use a paper wallet if you want to use coldstorage and going long term on them. Most alts offer their own method/ service to create paper wallets. Those wallets can only receive and not send funds, so you would have to import the seed from the paper wallet to the wallet client (eg desktop wallet) of the particular altcoin and restore your wallet there to be able to send the funds out of this wallet again.