I know it's often possible to get to Seattle in less than 4 hours, but I'm always thinking of the worst-case scenario. I've used the QuickCoach and other bus services in the past, and sometimes the border takes a long time, because the staff decide some passenger deserves close scrutiny. This is the type of thing that makes me very nervous when I'm about to head off on a flight. But it's definitely worth considering to save money.