How often you water over the winter will be partly determined by where/how you store your tree. A few examples:
Last winter (2006-2007) I had a Juniper that still had an intact root-ball from the nursery container. I simply removed the plant from the container in the fall and planted it in my growing bed. The tree was watered in well and once winter set in I ceased all watering until I dug it the following spring.
This year the same tree had been re-potted and would no longer maintain an intact root-ball if removed from the pot so around Thanksgiving I found a sheltered location on the ground and mulched the tree in well. Again no watering so far this winter. However due to a lack of enough snowfall to provide the expected insulating layer and a recent cold snap I just moved this tree, and some others, into an unheated garage.
I have other trees in this space and those have been watered several times so far this winter. The larger the pot the less often water has been required, some only a few times so far. Smaller pots have been watered more frequently. Some young Pines that are in pond baskets with 100% inorganic mix have been watered the most often of all, perhaps every other week.
The tree hasnt had water in about 3 days, I wonder if I should be continuing to water every day?
This sounds excessive to me. How did you determine if the tree needed to be watered that often?
I am only worried about the fact that after watering, when I put the tree back outside, the water will freeze and damage it.
Water during the day when the pot is not frozen this allows excessive water to drain before nightfall. Why would you not simply water the tree in place rather than move it back and forth unnecessarily?
Can you give us some more information about how you are keeping it. I'm worried that you have watered it too frequently.