After a bad windstorm, our power was off for nearly two weeks. It was rather like camping inside our own home. We had to heat water on the stove because the water heater had an electric pilot. We used tons of batteries for flashlights, cd players, and radios. We used old fashioned sponge rollers in our hair since we couldn't use dryers or curling irons. It wasn't fun, but we survived.
Probably a couple weeks on the farm when I was young. Had 10 ft snow drifts as well. The heat was propane so no problem there. Kerosene lamps for light, got water from the windmill in the pasture and melted some snow. Used the old outhouse. Always had plenty of food so that wasn't a problem. Took the stuff out of the freezer and put it in a snow drift. As a kid, there was plenty to do when it came to playing in the snow. Helping and caring for the chickens, horses and cattle was a bit tougher though.
The longest time I remember was 6 hours - rough guess.