So, I'm using vanity gen to generate the address (https://bitcointalk.org/index.php?topic=25804.0) on veery old offline computer, No wifi, no LAN cable, fresh installed OS, then I print the address detail such as private key etc. what I do next is adding that address to blockchain.info as 'watch only address'. what I ask is.. Is that address cold enough? I never import the private key anywhere.