12 would suffice for now, unless computer speed were to increase exponentially. For those who want to do the math, say that you were to use an alphanumerical passwords with casing, symbols, and ALT+characters. Alphanumerical passwords with cases alone allows 62 different combos. Add that to about 10 symbols and ALT+characters and thats 82 different combos. Since the password length is 12, calculate 82^12, which is about 100,000,000,000,000,000,000,000 different combos. If a cracker managed to take over 10,000 super computers, each capable of trying a billion passwords per/s, it would still take about 100,000 days to crack. But say that halfway between all those possibilities lies your password; that would result in your password being cracked in 50,000 days, or about only 150 years.