Doing the 1/2 and so far my longest run was just over 11. This weekend I'll be doing 12 and then probably wind it down. I run 4 days a week with short runs around 4 miles. I get up at 5:30 to get my run done before my husband goes to work (short runs).
I know it has been cold, but once I get moving, I really haven't found it to be too bad. I wear fleece lined pants, a thinner long sleeve shirt, a fleece lined running jacket with zipper so I can control my heat. I don't wear gloves because my normally cold hands get crazy warm. I do wear some sort of head gear (hat or headband). It really isn't that bad.
I do think the regular short runs have helped with my stamina. Now, if I could only get my shoe issue resolved, but that's a topic for another thread.