Books like Planet of Exile

The Earth colony of Landin has been stranded on Werel for ten years--& ten of Werel's years are over 600 terrestrial years. The lonely & dwindling human settlement is beginning to feel the strain. Every winter--a season that lasts for 15 years--the Earthmen have neighbors: the humanoid hilfs, a nomadic people who only settle down for the cruel cold spell. The hilfs fear the Earthmen, whom they think of as witches & call the farborns. But hilfs & farborns have common enemies: the hordes of ravaging barbarians called gaals & eerie preying snow ghouls. Will they join forces or be annihilated?