Unfortunately, none of the provided sources mention an expiration date for Yervoy discounts.

The first source [1] provides information about the patent status of Yervoy, but does not mention any discounts or expiration dates for discounts.

The second source [2] discusses the top 15 blockbuster patent expirations coming in the next decade, but Yervoy is not listed among them.

The third source [3] is the website for the Health Resources and Services Administration's (HRSA) Office of Pharmacy Affairs, which provides information about the 340B Drug Pricing Program. However, a search of the website did not yield any information about Yervoy discounts or expiration dates for discounts.

It is possible that Yervoy discounts may be available through specific healthcare providers or programs, but further research would be necessary to determine if this is the case and if there are any expiration dates associated with such discounts.

Sources:
[1] https://www.drugpatentwatch.com/p/biologics/tradename/YERVOY
[2] https://www.fiercepharma.com/special-report/top-15-blockbuster-patent-expirations-coming-decade
[3] https://www.hrsa.gov/opa