OK, let's assume you can try 1 billion (10^9) keys per second. Now add numbers to your keyspace (remember, no special characters or capital letters yet!), and make your password 12 characters instead of 8. Not much harder for you.

But now it takes 150 years to brute-force the keyspace.

I doubt anyone is going to devote 150 years of computer time to someone going through customs.