I'd leave him out for as long as he wants to be out in the snow - but not without a fence yard. As Tanza said, it only takes one car – or one annoyed neighbor -- to take him out, and he won't be adverse to taking on coyotes, so why risk it?
Most people seemed to have huskies or malamutes when I grew up in Alaska and they were seldom indoors. They'd even curl up and go to sleep in the snow, while it was snowing, and remain under a blanket of the stuff!