"Not to the extent of tracking down caches, but I know if I found a cache lying about near an ancient site I would treat it as I treat all litter near those sites. I'd dispose of it in a bin."
And so you should - if the thing is on display, littering the countryside.
"Hide them well out of the way and they'll be fine, in my opinion."
They usually are very, very well hidden - normally the only bit of plastic you can't find.