Bob's right that that's winter. Perhaps ask on the Thorn Tree forums for people with experience on the trek in those months. I've met people who hiked in December. It sounded rough, snowy and cold, but they did it.
That's plenty of time for the trek. I did the Circuit, Tilicho, Ice Lake and the Sanctuary in 17 days. Faster than most, but not the type of miles that I walk in the USA. Of course, the more time in Nepal the better!!
Many are choosing to take jeeps down the Jomson Valley. There is a road. Do you really want to walk a road? I did. Most don't.
In some respects, I consider the Annapurna Circuit to be dead or dying. They've built roads on one of the world's most famous treks. Does anyone know if the road up to Manang is finished yet? I suspect it's close. Then, the Circuit will truly be dead IMO.