Unless your forum is covering a subject that doesn't have a sustainable interest (ie if it's a forum about a TV show thats been canceled, a game that nobody plays anymore or a product that is no longer made/used for example) then it may be time to start to think about a new forum covering a new subject.
However, if your forums subject is something that people are always going to have an interest in and where there is always something new to discuss then keep focusing on that forum and try to bring it back to life. 250,000 page views a month isn't a bad block to restart your community from. Start promoting it more and updating it with new content and interesting posts and try and run some contests or something to really regenerate some interest. Try and offer your current member base a reason to keep posting and give new potential members a reason to sign up
Basically from what you've told us so far I would say it all boils down to what your forum is about and then deciding weather your forum has past that subjects "shelf life". You should definately try to make the most of your current traffic though!
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