I bought some melamine plates and bowls for using when I have lots of people around. They worked fine.   My question is: What is the safest way to store them? (They will be used infrequently, maybe every six to twelve months).  (I looked on Google without much success).  I thought of two options:   Put away in a cupboard, uncovered (the top ones might gradually get dusty) Store inside a plastic freezer bag, and the put into the cupboard   I was wondering if the plastic bag is a bad idea? It is intended to keep them as clean as the day they were put away, but maybe the melamine needs to breath or something or it might develop a funny taste? 
Although there is a known problem with so-called melamine furniture and shelving off gassing of formaldehyde, the source is the particle board within, and not the melamine veneer.  Melamine dinnerware — often known by the genericized brand name, melmac — is by itself quite stable.              Either of your storage options should work just fine for melmac. Assuming your cupboard has a door that's kept closed, the dishes might not accumulate very much dust. However, you could use a paper, plastic, or cloth towel or bag as a dust cover — or else just rinse off the top dishes before you use them.  If you decide to seal the melmac in a freezer bag, it will not suffocate and should be just fine. Just make sure it's absolutely dry before you seal it up. 