We have been going to Florida for seven winters now, five years with a Jayco and two with the Crossroads Cruiser. We leave at different times (anywhere from November to late December), but it is usually quite cold when we go and the unit winterized. Like fhenn said, load everything except the freezables beforehand, then add those at the last minute.
We do not run our furnace on the road. We find the freezables fare just fine. I put all the stuff in boxes and place them in the shower for lack of a better place.
We actually stay in our trailer the two nights on the road. The first night we are in Virginia and the temperature us usually around the freezing mark. The second night is in Georgia and it is milder. We leave the unit winterized and carry water in jugs for flushing the toilet and brushing teeth, etc.
When we arrive for the night at Walmart, we turn on the furnace, put the cat in the trailer, and go for dinner. By the time we get back the unit is nice and warm.
We have never had a problem. No need to pay for motels and schlepp your stuff in and out. We both drive the rig so we do 12 hour days and it takes us two and a half days to get there (Tampa area).
2012 Cruiser Sahara 330SS
2015 F250 Super Duty diesel