If its a 3 lane highway I stay in the middle lane regardless of my speed just to avoid people merging who do not know how to do it. This is of course just when on ramps are coming up. If its miles to the next one I'll get back over in the right lane.
Merging is a serious problem with the majority of drivers. They simply do not understand they need to be at the highways minimum speed by the time they merge. They also do not understand the car that is already on the freeway has the right of way under all circumstances and they need to avoid it.