Well, lets assume the worst case scenario, with it being a 16 character long password. You don't have to worry about the first 8 digits, so we can cut it in half. That would leave us with 1.8446744e+19 (256 ^ 8) different possible combinations, and that's just assuming only ASCII is allowed. If the encryption algorithm allows UTF-8, you'd be here for the rest of your life, although, I doubt you would have used any of those characters even if it did allow it.