Margarita mix stays fresh for up to 12 months. The mix should be refrigerated after it is opened. Margarita mix may start to change color or texture after 12 months.
If the mix starts to develop an odor, it should be thrown out. Margarita mix is likely to last past the "best by" date on the package, as long as it is stored properly. Margarita mix can be stored in the pantry until it is ready to use. The mix can be used to make classic margaritas or a number of dishes. For instance, the mix can be added to cheesecake filling or cupcake batter.