We spent some of this winter on board in Rhode Island
, but we hauled the boat out in Mid-December, and moved back on board the first of March.
This past winter is probably a bad example, but I think that it would have been really, really miserable for a couple of months, and I'm glad we decided not to be here.
We have a pretty big hydronic diesel heater, so can keep the boat at 70 even if it's in the teens outside. Even with that system running we were battling condensation
in a big way when temps outside were below freezing. Our boat's probably about average on the insulation
front. Dehumidifiers do very little.
I guess that's the main issue, battling the moisture inside, assuming you can keep the boat warm. And, as others have mentioned, beware the icy docks. Falling off of one into the water could be seriously bad.
Also, you will be carrying water to the boat, and will have to shower
somewhere other than on board (the moisture again). Pumpouts can also be a problem, so you might have to bundle up and hike up to the marina facility every time.
So, in summary, I think that it's fine to push the season pretty far beyond the norm on either end, but the dead of winter (especially if it's one like this year) you might find to be a bit much.
Of course, we might be wimpier than you, too!