well, kujawski...the answer is plain ans simple.
if you eat 5kg of potatoes daily for the next five days, then they will all be gone after that period of time. If you only eat 2kg daily however, you are stuck with them for almost a fortnight.
Personally, I would visit here
http://www.cookitsimply.com/category-0020-0k15 5.html and have a potato fest, say 12.5kg today and 12.5 kg tomorrow, perhaps choosing a variety of recipes to make the task less onerous.
My advice would be to, next time, consider a smaller bag.
Hope this helps. Te he .