If I'm going 80 mph and the flow of traffic/speed limit is 70, instead of swerving back and forth to repeatedly pass people, I would stay in the left lane while I'm passing groups of cars UNLESS I see another car behind me going even faster. In that case I would move back into the right lane to let the guy pass. Not saying I would stay in the left lane the whole time...if there was a big break in traffic, I would move back into the right lane and stay until I had to start passing people again.