This brings up the question of brevity. The most common expression you hear about advertising is that people will not read much. Yet a vast amount of the best paying advertising shows that people do read much. Then they write for a book, perhaps — for added information. There is a fixed rule on this subject of brevity. One sentence may tell a complete story on a line like chewing gum. It may on an article like Cream of Wheat.
But, whether long or short, an advertising story should be reasonably complete.