Just because something worked once doesn't guarantee it will work again. A few dollars worth of testing can save thousands later. Make sure others like the products or service as much as you do. They know where it all is because they never move it. Even if the population in your part of the world isn't growing, its still changing daily.
People move, die change jobs, etc.
All these things affect your customer base. If customers don't hear from you they will forget you. New or expanding businesses will aggressively go after your customers. Take a good look at your business from the customers point of view. This is the hard part.