There is no information available in the provided sources about restrictions on stacking Advil coupons. However, it is important to note that the sources are not related to coupon policies for Advil. The first source is a drug patent website that provides information on the active ingredients and expiration dates of Advil products. The second source is the official website for Advil, which provides information on the different types of Advil products and their uses. The third source is an article about a scrap metal reseller who pleaded guilty to filing a false corporate tax return and is not related to Advil or coupon policies. Therefore, it is recommended to contact the manufacturer or retailer directly to inquire about their coupon policy and any restrictions that may apply.

Sources:
[1] Drug Patent Watch. Advil Trademark Details. https://www.drugpatentwatch.com/p/tradename/ADVIL
[2] Advil. https://www.advil.com/
[3] Department of Justice. Scrap Metal Reseller Pleads Guilty to Filing False Corporate Tax Return. https://www.justice.gov/opa/pr/scrap-metal-reseller-pleads-guilty-filing-false-corporate-tax-return