+1
I've been giving that advice here for years. It's nice to have someone else beating that drum.
It's not unlike those cyclists who think they can buy speed, then find out they have to work for it. You can't buy warm, you have to adapt to the cold. I begin that process every October.
The one thing I can definitely say is that it is amazing just how little you can wear and still feel fine. I like your statement about beginning the process in October. This past fall I had quite a few shocking rides that I never expected I would have. The one in particular I can remember QUITE well was heading into the library one afternoon to get online. It was in the mid to upper 40s so I didn't think a thing about only wearing cycling shorts and a long sleeve thermal top. A couple of days earlier I had finally purchased a fleece headband that would fit all the way over the ears. I had seen keeping the ears warm was the one thing I needed to find a way to do without also keeping the head warm. I hadn't taken the fleece headband with me or the fleece mittens.
As I left the library around sunset for the 5+ mile ride home the temp had dropped a bit...I didn't realize how much until after I got home and looked. I remember thinking as I was riding home that if I just had the fleece headband and the homemade fleece mittens I could keep riding all night long with the temps the way they were. I was quite comfortable.
I got home and walked inside and headed to the kitchen window to take a look at the thermometer that hangs all day long in the shade right outside the kitchen window. I almost had a heart attack when I saw the temperature. It was onlu 36 degrees out. That is when I started to realizer just little I needed on to stay warm while biking.
You really don't think that the energy/heat you are creating from pedalling would be create enough warmth to keep you warm while moving so fast and creating such a wind chill factor. It doesn't take as much as what you think.
Unfortunately by looking at the 15 day weather forecast for NH it doesn't look like I'm going to get a chance to try to break my -5/-3 degree(depend on which temperature reading you want to consider) mark this winter. I definitely will try colder, even when doing long miles. I figure I will have to wait until next winter though to get the chance. The interesting challenge is the short hop/skip/jumps that only last 30-45 minutes at a stretch. I might be stupid enough to try -20F in that kind of cold if I got the chance. Heck I've ski jumped in -20F temps why not ride a bike in that kind of cold?