Unless FE is suffering I'd leave it in. I've also been told that you can soak an 02 sensor in Sea Foam over night and it will clean it, but I've never tried it. It shouldn't hurt the sensor since Sea Foam is 02 sensor safe.
I've wondered if there is a way to give new life to old sensor. Boy I wish I still had my old one. Flaming loaves. I actually ended up buying another one from someone on these forums. You'll be sure to hear all about it when I get it in this weekend.