Off to watch Warehouse 13
It's an OK show. The concept is amusing, but the writers are so slow about their plot arcs, and the characters don't have much room for development.
Only a little though...and there's a story element that I can't tell you about yet that could explain it. The only time that it creates a noticeable question mark is one particular room where there's piles of them, then it's possible to repair a good chunk of your health bar by chowing down. Similarly, there's a gene tonic that lets you do the same with alcohol, which is nice, considering the number of bars there seem to be in Rapture.
Potato chips don't really expire if still sealed; I would guess they just start tasting bad. They would taste bad, sure, but if still in original packaging they wouldn't kill you.
It's only been at most two years since the disaster at the Kashmir Restaurant. That was New Year's Eve (start of '59). Jack gets to Rapture in 1960. Still though, that's a bit of a while.
I have three theories:
1) The potato chips are vacuum sealed and have nothing in them to degrade them.
2) Rapture, being the society of the future, found a way to infinitely preserve potato chips.
3) Jack is using all of these Rapturian medical devices, which supposedly prevent you from getting sick, repair serious injuries, etc.
For a real challenge, try explaining the creme-filled cakes.