Reef Nutrition products do NOT have an Expiration date, instead they have a Best If Used By date.  This is an important distinction.

When you buy a quart of milk it has an expiration date, and shortly after that date it starts to smell bad and you toss it.  Reef Nutrition products don't expire in the same way that milk does.  As they get close to their Best If Used By date the nutritional quality slowly starts to fall.  Eventually the product will start to degrade and expire, and will develop an unpleasant odor. 

Would I feed Reef Nutrition products that are 2 months past their Best If Used By date to my tank - Absolutely, provided that they still smells like they did when you first received them.

Storage temperature also plays a role in product shelf life.  The colder the products are stored (except the live Tigger-Pods) the longer they will last.  Products at our facility are stored at 33 F (1 C) for maximum shelf life.