Those back mount gauges are very susceptible to freezing. What happens is that water collects in the tube below the inlet port and when you drain the system it doesn't drain out. Then when it freezes, it permanently deforms or ruptures the tube and ruins the gauge. So, it's important to protect the gauge from freezing.
I bought a bottom mount and mounted it on a street elbow and it's been in service for 4 years without removing it in winter. However, if you notice my location, it doesn't exactly get really cold here.