how to increase post-harvest life of potato tubers?

Answer 1

Keep them chilled and dry as cool as you can-- not freeze-- chill.
Then you want to layer them with newspapers-- the fewer injuries to the spuds-- the better they keep. Check them frequently for spoiled spots-- any other potato that is next to that spoiled place will get it, too-
The old folks (pre electric refrigeration)-- used a root cellar for all those type things--potatoes, turnips, cabbage, onions-- but not near the spuds-- I don't know how long in months the spuds lasted-- but a root cellar was a necessity along with canning and brining.
Good luck

Answer 2

A correct answer has been given-here is more info that may help. Potatoes will sprout in temps above 50 degrees, using itself to feed the new shoots, it slowly withers and loses its firm state. Dry is essential as well as dark-potatoes exposed to light build a layer of green under the skin which I have heard should be removed before eating. Since I don't know what variety of potato you grow, some are better keepers than others. Varietys available are many. Like onions, early spring types such as the Walla Walla Sweet, Texas Sweet etc., have little to no storage life. Check with your local USDA or County "Master Gardener" office, they have free or low cost 25 cents-$1 publications that are very useful on any subject matter. Hope this can help.