Unfortunately, the sources provided do not contain any information about Advil rebate offers and their expiration dates. The first source is a drug patent database that provides information on the legal status of drugs and their patents. The second source is the official website of Advil, which provides information on their products and usage. The third source is a coupon website that offers discounts and deals on various products, including Advil.

Therefore, it is recommended to contact Advil's customer service or check with the store where the rebate offer was obtained to obtain information on the expiration date of the rebate offer. It is also important to read the terms and conditions of the rebate offer carefully to ensure that it is still valid and can be redeemed.

Sources:
[1] Drug Patent Watch. Advil Tradename Details. https://www.drugpatentwatch.com/p/tradename/ADVIL
[2] Advil. Official Website. https://www.advil.com/
[3] The Krazy Coupon Lady. Advil Coupons. https://thekrazycouponlady.com/coupons/advil