Porcelain crown stain a couple days after cemented in. What are my options?

I just had 8 crowns cemented in last week. I noticed that it already looked stained. I wondering if my dentist have missed a step before cementing it in. Is this common? I have done some research and porcelian are supposed to be more resistain to staining then other material. I have an appointment with my dentist and she said will remove the stains by polishing them. I'm worried that it will be temporary and have to keep polishing quite frequently. What ate my options?