I believe that the fifth ball goes up at 1000 posts, but I'm not 100% certain. You might want to check some of the top posters over on the football board, which uses the same system. (The way you're going, you'll be there very soon
Runs for correct trivia answers are awarded by whoever asked the question, not by me. Whoever asked the question receives an automatic notification that an answer has been submitted, and they'll check the answer the next time they drop by. Nice answers, by the way.