Better stock up, quick!
Luckily, the shelf life is pretty well infinite.
They should make fine post-apocalyptic trade goods.
(Low-fat Twinkies, however, are An Abomination Unto Nuggan, or at least Unto the Goddess. This was experimentally confirmed several years ago when someone tossed a low-fat Twinky* onto a fire as an offering, and it wasn't accepted. Just sat there amid the flames, and eventually started leaking a bit.)
*That is the correct singular of Twinkies, right?