Discover the New World 51 FIGURE 3.9 Reviews. of your apps, or purchase additional functionality within your apps, or even just click on your banner ads. I call the 10-second impulse buy together with the 30 seconds to become a customer the 10/30 rule. It's incredibly important and I design all of my apps based on this concept. TRAITS OF SUCCESSFUL APPS Every success story differs, but the most successful apps share quite a few common traits. The following list gives you an idea of most of those traits. In the next chapter, I talk about how to use this list when you are brainstorming for app ideas.