Lipitor is a brand name for the drug atorvastatin, which is used to lower cholesterol levels in the blood. According to Drug Patent Watch [1], the patent for Lipitor expired in 2011, meaning that generic versions of atorvastatin are now available. The length of time a person should take atorvastatin depends on their individual health condition and cholesterol levels. As the NHS [2] explains, atorvastatin is usually taken once a day, and the dose can range from 10mg to 80mg per day, depending on the individual's needs. The medication is typically prescribed for long-term use, and patients are advised to continue taking it unless instructed otherwise by their doctor. As Blink Health [3] notes, statins like atorvastatin are often prescribed for life, as stopping the medication can cause cholesterol levels to rise again. However, patients should always consult with their doctor about the appropriate length of treatment for their individual situation.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.nhs.uk/medicines/atorvastatin/how-and-when-to-take-atorvastatin/
[3] https://www.blinkhealth.com/blog/how-long-will-i-need-to-take-a-statin-for