I also have a question regarding this same topic. I have an almost 3 year old colt who is still very sweet and not hard at all to handle. I have been working with him since he was 6 months old so he knows me and I know him well. He only acts like a stallion when we go to a show or he meets a new horse. Even then it is just squealing and some pawing. So far it hasn't been anything too difficult to handle. My question is, has anyone had a stallion suddenly become more agressive after three or would he already be exibiting these traits by now? One thing that may be prohibiting these tendensies is that he only has one decended testicle and the other one is no where to be found. I will eventually get him gelded, but I am in no hurry. The vet says there is no danger leaving him a stallion and he is nowhere near any mares so he won't be breeding. I know that keeps me from showing him so I do plan to geld him as soon as I can get the money together, but as he is right now he is the sweetest baby.
Laura