Based on the information provided, I was unable to find a specific recommendation for how often to schedule lipitor (atorvastatin) liver tests. However, it is generally recommended that liver function tests be conducted before starting a statin medication like Lipitor, and periodically thereafter [1]. The FDA recommends liver enzyme tests before starting a statin, and as clinically indicated thereafter [2]. The specific frequency may depend on various factors, including individual patient risk factors and the discretion of the prescribing healthcare provider. It is important for individuals taking Lipitor or other statins to discuss any concerns and questions about monitoring with their healthcare provider.

Sources:
[1] https://www.ncbi.nlm.nih.gov/books/NBK64821/#ch3.s3
[2] https://www.fda.gov/drugs/postmarket-drug-safety-information-patients-and-providers/questions-and-answers-atorvastatin-calcium-lipitor-and-risk-liver-injury