I personally do not agree with this idea at all. Threads are supposed to eventually die, including popular and well made threads. How long a topic stays on the front page should depend on how interested the members are in the topic at the time, not how popular the thread is overall as a whole.
It has already been mentioned, but the best way to tell if people are interested in a topic is to look at the amount of replies as well as reading a few of the posts. If people dislike a topic, they avoid posting in it and it quickly gets bumped back to the latter pages.
Another post I saw earlier was one where members can flag duplicate threads. Each moderator acts differently on duplicate threads, but I personally have no problem with them as long as the original thread is bumped back. I would rather someone create a new thread talking about Puppies than for them to bump a 4 month old topic up that has 10 pages of conversation that nobody wants to skim through. It's like going on Youtube and replying to someone who posted their comment 8 months ago. It's just awkward.
