I also do not switch wormers around... that said, we do not routinely worm. Calves will get wormed when weaned IF they look unthrifty... We do worm all BOUGHT animals that come here due to not knowing what/where they came from. We buy a number of bull calves to steer, and make up groups to sell.
Cows seldom get wormed unless they are going through the chute and look a bit thin or rough hair coat or something. If they are consistent problems, they get shipped. We try to have cattle that have a more natural resistance to worms and can thrive and produce without constant interference. We will do a routine worming of 1st calf heifers as they often seem to be the ones more likely to have worm problems and they are still growing and are bred back and can use to have a "clean gut tract"...
I have had several manure samples from cows, all different ones from fat shiny cows, to thinner or rough coated animals, run through for fecal samples for worms over the years. After awhile you get a feel for who might have a problem... and we do not spend a fortune on constant regular worming. It also helps to prevent the resistance build up if you do not use it often....
Every farmer has a protocol and you have to do what works for you. We used to give pinkeye vaccines and over quite a few years found no more and no less incidences of pinkeye and a couple of years seemed to have more cases... So we quit doing that also. And we have no more cases of pinkeye in the hereford and her x cattle than in the straight black ones. Some people swear it is the only way to go. One thing, we have found that home raised heifers out of cows that have been here a long time or raised here also, tend to have few problems with pinkeye and we cull more calves out of pinkeye problem cows... Bought cows mostly always have pinkeye problems before our own do and I attribute that to ours having an innate increased resistance to pinkeye, and all the "bugs" that are natural to our place. Natural immunity and resistance; it is like they tell you don't drink the water in Mexico, but the locals are well acclimated to it and whatever is in it...
Not saying that you shouldn't worm or use pinkeye vaccine... I believe that
@TCRanch has a pinkeye vaccine that the vet has made up that is autonomous to her own farm and animals....