[Porsche-O-Phile]

It usually takes a couple of days of sub-freezing temps to cold-soak piping to the point where it can really be an risk (larger diameter pipes are less susceptible). If you’re getting five days of marginal temps (cycling between being above and below freezing for a few hours at a time) I wouldn’t worry too much. Hose bibs should be shut off - those fail first. You can put plug-in heat trace on the more vulnerable piping if you think it’s going to be sub-freezing for continuous, uninterrupted periods. An old trick is to use incandescent light bulbs really close to piping / pumps where they can put out just enough heat to get the pipes warm.

Or put a bullet heater in the shed - they’re relatively cheap and can keep it just warm enough without burning through too much kerosene / diesel. I did something similar in a pool house I had (old, uninsulated) at my old house in the northeast years ago. Never had an issue and it just required a full-up every week or so (more if bitterly cold). It had a t-stat on it so I could keep it about 35° in there.

Best of luck.