Food, glorious food! For a while, anyway. Or if properly refrigerated. But when food goes bad, it goes bad—as demonstrated in this time-lapse video of the rotting flesh of dead animals and fruits we call dinner.
For the record, I have eaten donuts as old as two years. I was going for three with another batch, but cereal moths got into the box and reuined it.
The trick to mummifying donuts is to remove the grease so it doesn't go rancid and the water so it doesn't mold.
This is best done by loosely wrapping the donut in a piece of paper towel and letting it sit. Initially, change the paper towel daily, as the grease is wicked out of the donut into the towel. When the grease stains get smaller, you can change the towel less frequently.
Donuts that are frosted on the top are particularly interesting. As they mummify, the frosting stays the same size, but the dough shrinks. Eventually, it looks something like a mushroom.