I have a boy that was off feed for almost a year, started eating again for 2 months, and then stopped. He's not losing any weight, but he is driving me insane. I got him April of 2012, he stopped eating in October, started eating again in July, stopped again in September, and has shown no interest in food since then. He doesn't lose any weight, and has been hovering at about 500 grams for more than a year. He's definitely out of the norm, though. Usually males going off for the fall and winter is more common, anywhere from 2-5 months is fairly normal.