why can't you write the keys down, or destroy the printer?
write down a private key is a bad idea, you write a 0 rather than an O and you have simply f**ked up your bitcoins, in this case an electrum seed can avoid lot of problems and it also contain unlimited addresses.
You can for sure destroy a printer, but who knows if an attacker has already stolen the private keys? (dumping printer cache, man in the middle, etc...)
Practically unlimited. Of course it is still limited by the actual entropy of possible bitcoin addresses. But yeah, electrum is a nice way. Although using it on an online machine makes it prone to the same old attacks.
