As far as dealing with threads that become "outdated", I think allowing them to be pushed farther back is enough. For example, the Sim City Prototype thread would be pushed farther down/out of the first page over time, assuming enough new threads were coming through (the goal we hope to achieve). Similarly, with modern games becoming retro, by the time something such as PS4 becomes "retro", the first 5 pages of the modern forum (at least) should no longer hold PS4 threads, so I think rearranging the threads at that point is just creating work for no reason.
Of course, I don't have to make mod decisions, so I could be completely wrong.