making a secure bitcoin wallet which is always offline and stays that way is not really hard, and i am talking from 2 years of experience with having only one bitcoin wallet on an offline linux system.
That means u dont use your bitcoin. For those who use bitcoin regularly, needs to wallet... one online and one offline.
Like the bitfinex's cases, I don't think a lot of their member are online at the time bitfinex are gonna get a hacked by someone. online or offline need more researching about the wallet of bitcoin have you used it. but if using the offline wallet I think that is always secure in your wallet online or offline.