Now I have. I see that one species in the show looks like a Night Fury.
Being unable to survive in consistently cold habitats I'm not so sure about if Berk really is cold most of the year as Hiccup sometimes claims.
Dude I agree with what your saying about the Night Fury's weaknesses because we've seen Toothless survived in cold enviroments in "Snow Way Out" and in "Dragon eye of the Beholder". Not to mention the fact Toothless has flown many places without resting.