Freeze them.

Pack whole, sliced, or mashed. Freeze medium to large mature, sweet potatoes. Sort by size and wash. Cook until almost tender in water, steam, or oven. Let stand at room temperature until cool. Peel, cut in halves, slice, or mash. To prevent darkening, dip whole or sliced sweet potatoes for 5 seconds in a solution of 1 tablespoon citric acid or 1/2 cup lemon juice to 1 litre water. To prevent darkening of mashed sweet potatoes, mix 2 tablespoons orange or lemon juice with each litre sweet potatoes. Pack, leaving 1cm head space. Seal and freeze.

For variety, roll cooked sweet potato slices in sugar. Pack into containers, leaving 1cm head space. Seal and freeze; or, pack whole or sliced, cooked sweet potatoes in containers and cover with cold syrup made of equal parts of sugar and water. Leave head space. Seal and freeze.

Traditionally, sweet potatoes were stored by putting them in a box under the bed. My bedframe won't allow that, but I stored them, one year, in a box under the coffee table, and that worked fine.

Don't know if this would work with store-bought, though. They seem to go bad awfully quickly.

I refrigerate and they last a long time, as do regular potatoes. If your really concerned, yes, they can be peeled and partially baked, then frozen. Think of the partial baking as sort of a 'blanching'.

I'm going to try and freeze some. They are 25 cents a pound down here.