I also instinctively check my mirrors for cops. I don't drive too fast anymore, but I think it's a habit I have from when I used to speed a lot. Other than cops, I don't see the point in checking your mirrors very often when you're not changing lanes. What can you really do about the traffic behind you?I usually check my mirrors only when changing lanes. The only other reason I might check my mirrors is if I am going a little bit over the speed limit and want to check for cops.