This is correct as part of product validation the companies have to do shelf life testing to prove efficacy is maintained up to the expiration date that they state on the medicine.
There is a tradeoff between testing time and cost, time to get the product to market, actual duration needed to allow for product transit and time on shelf, and of course planned obsolescence.
A typical standard would be 2 years. I’ve always felt there was a market for someone to buy product and do life testing to double or triple the amount of time to prove efficacy beyond the time that is advertised. Then they could publish this information and request authorization from the government to relabel old stock with the new dates.
If the worst happens and they start removing Ivermectin from the shelves and make it prescription, I figure an expired product is better than no product. There are probably some human meds that “change” a year or so after the expiration date but I doubt horse Ivermectin will. If I needed it I wouldn’t be afraid to take it up to two years out of date.
The farm Vet that comes to treat our goats said that he’s hearing rumors about the government making common OTC pet and livestock meds prescription. He said we needed to stock up just in case. I’m sure Ivermectin will be one of them if it happens. We also keep Teramycin on hand for eye infections, etc. in the goats and the dogs so we will buy a few tubes of that.