As others have stated BWI is not an overly large airport.
SW has one of the most highest profile concourses in BWI, and most conveniently located, however it is all of concourse A and B. So if you have to get from one end to the other, you could have a long walk.
Also, if it is 30 minutes from your plane landing, you will never make it, especially if you are in the back of the plane.