Before I get into overnight freezing conditions during storage periods. For me it is not a once a year thing.
Since our camping season overlaps winter storage conditions, I often winterize 2-5 times. After an October campout. Dewinterize for a November campout or road trip, winterize again before storage. Dewinterize for a trip south in January-February, winterize again before storage. Dewinterize for the the March campout, winterize again before storage (late spring is tricky here). Dewinterize before April campout, drain tanks and blow lines before storage (late spring is tricky here).
Winterizing doesn't cost that much in time, effort, cost of materials. Washing the RV is a bigger effort.
I've lived 20+ years in southern Michigan. The climate is different. I would winterize for going into storage anytime after mid-October, and any time before going into storage before mid-May. The last year I lived in southern Michigan, we had a deep freeze and foot of snow on May 1st, after six weeks of what looked like spring weather. For RV plumbing safety, you need to base your winterizing schedules on climate record extremes, not monthly averages.
Conditions when camping (and running heating systems) and during storage or cold transport are two different issues. While I might use my RV unwinterized in winter conditions, for storage it will be winterized.