How Long Can You Keep a Box Cake Mix?
Box type cakes mixes a generally good until they pass their expiration date printed on the box. As long as it's kept dry and in a cool place 18 months is about as long as it is good for.
Boxed cake mixes have different shelf lives depending on the type of mix cake and their manufacturer. Check the expiration date. Most boxed cake mix's shelf life is 1 to 3 years.