NOTE: When I say fannish, I don't necessarily mean "involved in fandom." I mean that I think about the shows a lot, the characters, may write fic, and get excited. In short, I get fannish ;)
I've been slowly breaking out of that mold. Currently, I'm having fun fannishly with SG-1, Smallville, MacGyver, Farscape, and now Supernatural. And the experience has been interested. I notice I am less obsessed with SG-1 (though that could be do other reasons and also the looong hiatus--I expect to get jumpy again in April), and while it's sad, it's also freeing. I'm finding I'm not stuck in a single mindset and that everything is about SG-1. I can watch other things, enjoy them, and it in turns helps me creatively. It's like when I read -- I jump from horror to fantasy to science fiction. It gives me the variety that I need to break creative blocks.
I've also moved past having a sole favorite show. If I want something different and a bit bizarre, I'll put in Farscape. If I want something nostalgic and idealistic, I'll watch Superman or Smallville. If I want something twisted with conspiracy, I'll put in X-Files. If I want something filled with archetypes and fantasy, I can slip in Star Wars. If I want urban legends and the occult, I can put on Supernatural. If I want wonder blended with science and history, I'll watch SG-1. There's something out there for every side of me :)
I know this isn't for everyone, but it's working for me :) And I'm not one to ever abandon something I've gone fannish for. I still adore X-Files. I still exalt Star Wars. And I'll always always love SG-1. I'm just having fun being able to dabble into all my interests.
Isn't being a fan fun? I get to squee about multiple things at the same time! Hee! :)