There's an old advertising maxim that a potential customer needs to see an ad 7 times (or 3 times) before acting on it, but it seems to be only weakly supported

There's an old advertising maxim that a potential customer needs to see an ad 7 times (or 3 times) before acting on it, but it seems to be only weakly supported by statistics. Maybe it's just something they say to get you to buy more advertising, but it does seem to make sense that repetition would increase the effectiveness of your advertising (remember the Head-On commercials? apply directly to the forehead!).