Based on the provided sources, it is unclear whether the Yervoy discount is time-limited. The sources do not explicitly mention any time limitations on the discount for Yervoy. However, it is important to note that the sources mainly provide information about Yervoy's effectiveness in treating specific conditions and its FDA approval status, rather than details about any ongoing discounts or pricing information.

The first source, Drug Patent Watch, provides information about Yervoy as a biologic drug but does not mention any specific discounts or time limitations [1].

The second source, a news release from Bristol Myers Squibb, discusses the effectiveness of a combination treatment involving Yervoy for patients with metastatic non-small cell lung cancer. However, it does not mention any information about discounts or time limitations [2].

The third source, the FDA label for Yervoy, provides detailed information about the drug's approved uses, dosage, and potential side effects. However, it does not mention any information about discounts or time limitations [3].

In conclusion, based on the provided sources, there is no explicit information about whether the Yervoy discount is time-limited. It is recommended to contact the manufacturer or consult with a healthcare professional for the most up-to-date information regarding any discounts or pricing for Yervoy.

Sources:
[1] Drug Patent Watch: https://www.drugpatentwatch.com/p/biologics/tradename/YERVOY
[2] Bristol Myers Squibb: https://news.bms.com/news/details/2020/Opdivo-nivolumab-Plus-Yervoy-ipilimumab-with-Limited-Chemotherapy-Significantly-Improves-Overall-Survival-vs-Chemotherapy-Alone-for-Patients-with-First-Line-Metastatic-Non-Small-Cell-Lung-Cancer-in-CheckMate--9LA-Study/default.aspx
[3] FDA Label for Yervoy: https://www.accessdata.fda.gov/drugsatfda_docs/label/2015/125377s073lbl.pdf