Some companies work in an entire state at a time and then move into another state.  That is why a variety of clients is wise to maintain an even work flow in your business.  Make sure you have a healthy mix of not only the types of work you perform, but also different types of businesses, i.e., a few national, a few local, firms, corporations, etc.  I try to alternate my marketing to 10 of #1 type business, then market to 10 of #2 type business and so on and then rotate back to the original types of business.  It seems to have really help offset when one type of business is slowing down, the other seems to be at full speed.