If you consider your random keyspace with 26 * 2 chars + 10 numbers + 20ish special chars then to crack 10 letters you'll have to try an average of ((26 * 2 + 10 + 20) ^ 10) / 2 = 6.8724016e+18 keys. If you then assume around 3 million hashes per second it still takes around 72641 days to crack your password.

Edit: As another comment said, just make sure it's not easy to guess based on rainbow tables and whatnot