Tricks to preserve chips (french fries)?
Here is an excellent recipe by the guys over at Cooking Issues (and also a follow up report) with almost everything you'd ever want to know about chips.  That first recipe is supposedly good even after they've cooled off:


  Our standard fries are good even when cold.


Another option is to cook a lot of chips but stop after their first frying and freeze them; when you want to eat them, simply put the frozen chips into the fryer for the second frying.  This also has added benefits:


  Freezing acts like partial dehydration. When the frozen fries are finished, they liberate water freely, leading to rapid dehydration and good crust formation with a porous interior. Pre-frozen fries are crunchier than fresh and stay crisper longer after they are fried, but they tend toward hollow fry.