You may have heard that Twinkies will last forever. I decided to do my own research and see. Short answer: definitely not.
In September of 2010, I received a free Twinkie as a free sample at a store. I wasn't particularly hungry at the time, so I figured I would leave it in my truck for some time when I was. After it had sat there for a while, I reconsidered and decided to wait at least a year and just try it out. Well last night, nearly two years later, I finally cracked it open.
It was stale, obviously. The cake was very crunchy and difficult to bite through, especially on the bottom. The filling was even worse, having taken on a chewy, gum-like consistency. The flavors were still Twinkie-like but not very pleasant. I could only stomach half of it. Luckily, I haven't gotten sick from it. Actually it seems surprising that nothing was able to grow on the Twinkie, I suspect partly due to the high sugar content. Perhaps that has helped the urban legend.
Bottom line, they may not rot and they might look pristine, but Twinkies definitely have a fairly short shelf-life.