After much deliberation, the moderating staff and I have decided to introduce a new policy of closing any thread that reaches a total of 1500 posts. At 15 posts per page, that allows for 100 pages of discussion per thread.
There are a few reasons why this policy is being introduced, but the primary one is to help the moderating staff patrol some of our largest threads - a handful of which now span hundreds of pages. You'll also find that it takes an increasingly longer amount of time to load a page as you move toward the back of a thread, so this new policy should help with some performance concerns.
If you're participating in a thread that reaches this limit and ends up closed, don't worry. You're more than welcome to continue your discussion in a new thread and simply link to the old one as a reference for the topic at hand.