I knew a sister in my old congregation that had two sons and I actually studied with one. I left the org, went back to college, new job etc. Then I ran into her about ten years later at a store. After a brief how-do-you-do she excitedly told me how her now adult son had started studying again. I later calculated that he must have studied off and on for over ten or twelve years.
What's the longest bible study you ever heard of?