I've been hunting prickly pear/pincushion cactus country for about 45 years and have never put boots on any of my dogs, since they learn to avoid clumps of prickly pear pretty quickly, and pincushion cactus mostly show up in heavily over-grazed areas that the birds avoid, too.
In a dozen years of hunting real cactus country, in Arizona, I have avoided places with too much teddy bear cholla, since there are other places to hunt. But, all cholla drops pieces, and unlike the fuzzy teddy bear clumps, several other kinds turn brown and can't be seen as well by the dog. I booted my female Lab with Lewis dog boots, which she hated but tolerated, but have not put boots on my current dog, a French Brittany. After three winters in AZ he has become adept at avoiding some cactus and plants like catclaw. His feet take a beating, but not enough to cause problems hunting. I rest him after a few days.
You shouldn't have much of a problem in sharp-tail/sage grouse country, but I always carry a Leatherman just in case, to pull cactus spines.