With our zone difference in mind (I'm 7A) I'll just put in my 2 cents worth. I grow 90% of my daylilies in smallish pots. The small 6 inch or even smaller pots get overwintered in my ATTACHED unheated garage. Left outside they do not survive for me (the other larger pots (8"-12") are left outside in sheltered locations above ground). If you are going to take your daylilies inside, here's what I would suggest. Let them stay outside for as long as you can while letting the foliage begin to die back. When really cold temperatures begin to move in for days at a time I bring mine inside regardless of how the foliage is....... Dormant or mostly so daylilies require very little water. Think of all those daylilies sitting for months on end in Walmart without a drop. I wouldn't subject MY daylilies to mart store treatment but the point is, daylilies do better dormant with minimal water. Just enough to keep the roots moist. When the temperatures start to warm up in spring begin hardening them off before the foliage grows too much. I've had good success with this method and wish you luck if you try it...
......Maryl
