Sorry for the delayed reply but having been away, being thrown straight into work and having man flu I'm only just catching up!
Anyway, with the forum being quieter than it used to be, pretty much every "active" topic appears on the first page of each sub forum as it is, so I don't see a real need to start splitting down topics into even further sub forums. Sure you'll come back to a lot of posts after being away for two weeks, however those posts are concentrated into a relatively small number of topics. For example, the first page of topics in Rest Of The World goes way back to 24th November with thee IAAPA topic, European Attractions goes back to 25th December with the Plopsaland topic.
I see people's point on the coaster poll topics, but they're not really pushing down active discussion as mentioned above and they only really occur over a relatively short period of time during the quieter closed season anyway.