But, did you know that it takes the same time to boil one potato as it does 10lbs? On dinner days where I'm planning making mashed potatoes, I will cook and mash as much as an entire bag. After dinner, once we've used up we've eaten and the rest have cooled, I portion them into quart-sized freezer bags, flatten them somewhat for easy stacking, and put them in the freezer.
This tip takes VERY little prep time. Since making mashed potatoes can be a dirty job anyway, why not just make them in bulk and have one mess to clean? I'm a believer. Try it, and I think you'll agree!