My family got me one as a gift, it lives in the little slot under my hand brake. I had put it on my dash at first but it kept flying off into the footwell on any turns!
From what I've seen, most people keep the ducks, but you're more than free to pass it along.
Ducking is a fairly new thing that came with Instagram and Facebook, and its a mixed bag of people who like it and people who don't, seriously I've seen vids of a guy melting the things with a blow...
I don't have these fenders but bought cheap knock off plastics at one point for my old Tacoma.
You get what you pay for, the plastic faded in about a year, not really worth it.
I would keep an eye out for take off fenders or upgrade to one of the many flat fender options.