Cold storage of your private / public key combination in principle protects you against hackers but you need to be extra careful re

a) backing up your keys (if you only have it stored on a paper wallet and you lose it you lose all your coins)

b) physical theft of you paper wallet

In addition to encrypted wallet.dat files & cold storage paper wallets I have my keys backed up in the cloud in OpenPGP encrypted files stored in TrueCrypt containers (ie dual encryption protection).