Always a tasty treat. Ma usually whips up a batch once or twice a year, and they disappear as they get eaten quickly.
Most recipes for Haystacks consist of chow mein noodles, butterscotch chips, and peanuts, with a few variations here and there to make things interesting, like maybe a touch of cayenne pepper to spice 'em up, chocolate chips substituted or added in, peanut butter or marshmallows, or Heath Bar/toffee chips, etc...
The basics for fixing them are to melt the chips(and peanut butter if desired) in a microwave or double boiler, add in the chow mein noodles and peanuts, carefully mix it all together, then scoop out teaspoon/bite size clumps and place on wax paper or aluminum foil, allowing to cool, then eat.
I don't know how long the keep cause they never sit around more than a day or two at the most... :P