I had to go do some research recently when I noticed things like "shortening" suddenly had short expiration dates. In fact, things like shortening last pretty well forever if stored in a cool dark place.
Some item like dairy products and meats we expect to have use by the expiration dates listed. We know that a week after that date it's going to be bad. But what about canned foods or packaged dry goods? Well once they passed a law making it mandatory to have expiration dates and requiring producers to pay to prove the date, those dates no longer mean much. For every year they have to pay more so most only do 1 year testing but some will go up to a 3 year test level.
Don't be tricked to toss out that mustard or shortening because the expiration date is past. It's still good unless you left it out when it states to refrigerate. Here is a site that will tell you about expiration dates: http://stilltasty.com/articles/view/5
I store shortening for long term storage because it was created way back in WW1 times to last forever so they could feed the troops cheaper. Unused shortening stored in my dry cool basement could give us needed fats in a crisis. I mostly use coconut oil and olive oil. Coconut oil is another fat that unlike shortening is a very good fat and it will store forever. Olive oil has to be rotated and used so I only store about a 9 month supply so it doesn't go rancid. If it does go rancid don't toss it out! You can use it in an oil lamp.
I just wanted to make sure you knew those dates don't really mean that much anymore. So stop tossing all those cans and boxes and discover how great they still are past the dates!