Could be cooked.
For some years, from time to time I had failures with Apivar. I even complained here on the forum about it.
Then one day I had an epiphany, every time there had been a problem, that Apivar had either been stored where sun shone on it, or been in the cab in super hot temperatures for some time. Also, not sure if this was a problem or not, but to make sure I didn't miss any hives I used to walk around and put the required amount of apivar on the lid of each hive when I arrived at the site, then install it as I went. This meant that some apivar could spend an hour or more at lid temperatures too hot to put your hand on. Although I never for sure found if that was a problem but in any case I have stopped doing that since discovering the link between longer term heat and strip failure.
So what should you do? I would say don't chuck the strips, they just might be fine, and they do cost. Use them, but keep an eye on your hives and watch for any signs of PMS through the winter. If that happens, then change out the strips for good ones.