Potatoes store super well under the right conditions. somewhere about 10c to 13c or so is ideal. but even without that, i would imagine they'd last at least 3 months or so. i've seen charles Dowding store them in burlap sacks all summer long and well into fall
I've had good luck storing potatoes for very long periods of time, over 9 months, by being very careful about storage conditions. Onions, too -- but don't store the two very near each other.
