My boyfriend says parmesan sprinkle cheese is bad because it has been in the refrigerator for a long time. But I still use it long past it's date and don't seem to have any problems with it. What do you think?
Use-by dates are set as the very minimum time that the product in question will be good for, provided that it is stored properly.
In addition, and as a general rule, because Parmesan is a dry, hard cheese, with very low water content, the use-by date is almost always far shorter than the actual time that the cheese will be good for, again, provided proper storage.
By "parmesan sprinkle cheese", I assume you are referring to the ones that come in a parmesan-wheel shaped box, such as this:
Their shelf life is far longer than their expiry date, and I would not be worried about using it beyond that date. However, for those boxes, most manufacturers tend to use the youngest cheese possible (for Parmesan this means 12 months), meaning it has not had as much time to age (some parmesan is aged for as long as 36 months, and some manufacturers age it for even longer than that), meaning that there isn't much flavor in it.
Personally, I stopped using the boxes a few years back, when I realized that I used far more than I would if I simply used a grater and a piece of parmesan, meaning that it I spend less (if memory serves, I calculated the annual savings to something like 300 Norwegian Kroner/50 US Dollar) on parmesan, getting more, and I think better, flavor from it.
It should be noted that my family uses a LOT of parmesan (depending on how often we have guests, we go through anywhere from 1/4 kg to 1 kg per month), so the savings argument may not hold true for you.
It lasts a long while as long as it's stored properly. I use mine up too fast to have a problem. You may want to freeze half so you don't end up wasting it. It freezes very well.
Hard cheeses naturally contain a lot of salt. I buy the store brand and it contains no preservatives, just cheese and cellulose as a non-caking agent.
Cans of cheese sprinkles are made to be shelf-stable for a longer time than fresh or block cheese (often, this is because the sprinkles are not made with real cheese -- or, if they are, then they also contain a lot of preservatives). The sprinkles should be safe to eat at least through their expiration date if stored properly. That said, any fat in the sprinkles can go rancid and mold can take hold well before the expiration date. If the contents of the can smell bad or the color of the sprinkle changes, don't take any chances; the cost of replacing the can is far lower than the cost of sickness.
Kraft's website says they pasteurize or heat treat all their cheeses to kill bacteria and they are confident they are safe to eat. That includes their Kraft Parmesan grated cheese in the shaker container sold in the unrefrigerated aisle. Some brands I've seen don't say on the bottle "refrigerate after opening." Kraft does for legal protection, just to be safe from lawsuits because if you live in a very hot and humid climate (like Florida where I am), the opened container will absorb more moisture from the air and will begin to degrade sooner, also because of the heat. Hard Parmesan cheese was first mentioned in the literature in the fourteenth century, obviousy long before refrigerators were invented. So, as far as Kraft pre-grated cheese is concerned, any bacteria would have to come from an external source to begin to cause a problem, as the company claims it is sold bacteria free. The cooler temperature helps keep the flavor fresh.
The rule with hard cheeses is you don't want to eat the moldy bits. This is easy to avoid when the cheese is in a block because you can just cut the moldy part off. With already ground cheese, the whole can is suspect the second you see any mold at all. That said, the agreed upon time is 3 months past the date on the package. I've used the cheese for longer than that myself but I can't recommend doing so.