I use my camp occasionally in the winter. No running water inside but I do have a submersible pump with heated hose to draw water from the lake through a cut hole in the ice. The pump then fills up a 20 gallon water tank that I keep warm with a bucket heater. The Outdoor shower heats up nice Even when super cold out with a camping style on demand water Heater system.
Reliance toilet waste bags take care of bathroom issues or we take a trip to the mainland.
No issues with heat,... electric baseboard as well as mini split and propane fireplace get it toasty pretty quick. Having Wi-Fi thermostats is a big plus for getting the camp warm ahead of time!!
Oh yeah, the wife has never spent the night during the winter months and doubt she ever will. I mainly use it for ice fishing / snowmobiling, etc, etc.
Yes my camp is fully insulated.
Dan