I agree that it is a good idea to give coyotes, or as Tom says even beaver, a choice. I like many coyote trappers use 3 lures or so as my daily lures and a few more as changeups. I don't worry about yotes remembering my lures, because I will be trapping a "new" population next year.
In other words, for fur trapping, don't worry about coyotes getting use to your lures. A good lure or lures wil work year after year. Why? Simple- mortality rates are high for farmland yotes. Each year, you will be trapping mostly young of the year- a minimum of 80%, and my guess over 90% . These young have no experience with your lures or style of trapping.
Now within the same season, while you certainly can "spook" yotes from a particular lure, if you are using 2-3 lures you already have providing him a choice. A true spooked canine, I believe, vacates the area and avoids the sets,. He doesn't mess with them. (I believe strongly a true "digger" is extremely rare, but thats a different topic) A coyote is more apt to avoid your type of set. So if you want to try a change up late in the season- try a set you usually don't make. Lure this with something odd- mink gland, fish oil, etc- a truly new catagory of scent.