marketing question for those in very small markets

I am in a very small market, about 2000 households in a 3 mile radius. Is there a point where you kinda hit a critical mass and marketing kinda becomes essentially innefective? I have been around for 8 years and we do mailers to all the houses in the area and it was great at getting us going at first but now, other than a couple day surge, we just drop back into our normal sales. I’m just wondering if it is even worth doing paper mailings anymore as the town is small enough and people know we are here or if I am just mis-marketing my product. What are others thoughts?