What’s the longest you’ve maintained a ruse before others knew?

In high school I participated in a team-based competitive quiz game called “scholar’s bowl.” Our school’s scholar’s bowl team regularly traveled to tournaments hosted in towns scattered around the state. I was particularly valued on our team for my knowledge of science history.

Once while driving home from a competition, one of our team was quizzing us from a big science reference book he had brought from home. One whole section was devoted to the scientists responsible for various discoveries. I was on a roll during that part, getting nearly all of them right. But as the names and discoveries became more obscure I was reaching the limits of my knowledge.