[Ntrails]

5.5 years is ~173563000 seconds or my maths and google are both wrong.

For pure brute force you'd want to make some assumption about the mean time taken to find the correct password, but lets argue that you find it after checking exactly 1/2 of the possible combinations.

2.8400e+10 passwords checked in 1.7300e+8 seconds => ~0.6 milliseconds per check. ish. I think.

Edit: as comment below points out, humans are crap. In reality any hack would use dictionary attacks rather than pure brute force. I was just addressing the maths.