I've had the water freeze on my drysuit many times, typically I will get into a car to thaw out and then since my drysuit is a membrane suit it will pretty much dry up and not freeze up again. However, I'm always concerned about the regulator freezing in the process of swapping cylinders. Keep things in the water keeps them from freezing though. The valve, IMO that's probably one of the few things that you really don't have many worries over. Drysuits can crack, regs freeze internally, masks fracture, zippers rip out, there are a lot of things that can go wrong.