You say "my customers already know where I am". Consider the public - your existing and potential customers - is on the move, both literally and figuratively, and sometimes catching their attention is like hitting a moving target. Approximately 85% of customers live within an 5 mile radius of most businesses and 18.6% of Americans move every year. Potentially that is a loss of 18.5% of your current customer base. Add to that the fact that 15-35% of the traffic on a given street is "just passing through" (vacation travelers and such), and you can see the great potential for stops by those unfamiliar with the area.
We no longer live in a 9-to-5 society, and people will drive past your business location 24 hours a day. With a lighted LED Electronic Message Center sign, you have an opportunity to communicate with your existing and potential customer, even when your business is closed and you are at home enjoying your family.