I have never had any problems with my thread type nipples "striping out" during freezing weather. I haven't had the water in my pipes freeze solid though, which I'm sure is what could cause this to happen. My experience it that if kept properly heated and insulated the pvc pipes rarely will freeze, but since the nipples are exposed to the air they do seem to freeze.
I have mitigated this by using heat tape on the pvc and circulating warm water through through them at all times. Between the heater in the holding tank, the heat tape and some cheap foam insulation the water stays warm enough to keep my nipples at least half thawed out, depending on where they are along the pipe run. This all may be overkill to most people, but with night time temps around -15 -20 lately, it keeps my birds drinking.