Fortnite is several weeks into the first season of its fourth chapter. In real time, it's been going strong since the summer of 2017, and though Epic doesn't share player counts, by any available metric it seems to still be doing incredibly well. But in the live-service world, Fortnite's success feels increasingly rare. While there do exist other major successes in the pocket of the games industry where studios operate one game for years on end, many others are closing their proverbial doors...