I was added late to a project working on a training simulation engine, similar to games, where each avatar in the game was a separate thread... man, the GC pauses on the server would sometimes freeze for literally 10-15s, and it was not good at all. I refactored it to use an event-loop model and only 2 other threads, which ran much better overall. Even though it wasn't strictly a game itself, the techniques still matter. Funny how running through a list of a few hundred things is significantly better than a few hundred threads each with their own timers, etc.