I'm sure Canadians and those in the North do not use water in the winter, but could use only water to add to the tank in the summer, I'd caution against that.
Never...not in my washer, not in my radiator and not in my battery. I recall a few years ago when fussing around my '82 Volvo and realized the washer fluid in the tank was likely close to 15yrs old. Everything worked as should however, but the car is for show only and rarely gets driven. So I siphoned the fluid out (blue washer fluid), cleaned the tank including filter screen and replaced with brand new fluid...just for the sake of good maintenance.
On a side note, I am a big believer in replacing fluids when automobiles age, with the exception of transmissions. Replacing tranny fluid can sometimes create problems that never existed before. So for example when I purchased my Crossfire, it had just turned 4yrs old. I had the cooling flushed, oil changed (of course) and the brake fluid pumped and replaced. I find the most common overlooked fluid is the coolant that I would recommend flushing after say 80,000km (49,000mi). In all the years I have owned cars, I have never replaced a water pump, radiator, master cylinder, brake line or pump....