I think it all depends on the horse and how its used. I am going to start clicker training my new mare, because treats don't work for her, for several reasons. But normally what I do is some of pressure and release, and treats. I start out giving treats when they've done what I asked them to do, and slowly "wean" them off of the treats, the time it takes to do that depends on the horse, and then use more praise, and release of pressure and little to no treats. I do give treats just cause I can, the horse is standing for grooming, or I've had him/her in the wash rack for an extended period of time. I do know a dressage trainer in my area that feeds the horse a treat when she gets on, to teach the horse to stand still next to the fence so she can get on, as she's older, and can't just swing up onto the 17+ hand horses she trains. And then she gives them a treat after she gets off when she's done riding. My first horse did have a big biting issue, so I never fed him treats, and even then it took 3 years to get to the point where I could say with any certainty that he isn't dangerous to be around. I think that for some horses treats are a good reward, and others just the release of pressure is enough. Fortunately for me, my horse is 4, and has had very little human handling, so she is incredibly perceptive of my body language, and for her just the release of the pressure is reward enough. Sorry for the long post.