We use a mattress cover but go through them like crazy! We are averaging buying a new one more than once a year. Is this normal? I'm not talking about pads that protect the mattress from wetness, I mean just the normal mattress cover. We haven't tried anything expensive, maybe that's where we are going wrong. LOL. The last one was a Martha Stewart one from K-Mart. Is this an item that fits the "you get what you pay for" category?