SS; we keep our bulls for an average of 6-8 years. Yes, really. If they are 12-18 months when we buy them, then they are often here for 6 or more years. Realize that we rent alot of pastures, the bulls are put with anywhere from 15-45 cows on average. We run 2 breeding seasons, spring and fall, and not all of them get used every time.We keep an average of 8-10 bulls, and use 5-7 in the spring and 3-5 in the fall. We also lease out one or two every year to people who have been using them for several years who only have 15-20 cows and a bull is a big expense for a couple of months use for them.
The biggest problem we have had is feet problems. We did rent one pasture and had a neighbors bull get in and our bull wound up with a broken leg, figured his bull hit ours from the side when he was breeding a cow. His bull was a problem with several area neighbors, very aggressive and mean, so it wasn't us. Had one years ago that "broke his penis", but that was the only other problem. Did have one that came up shooting blanks after using him for 4 years, we just shipped him.
The only other problem we have is they get to where they just decide they won't stay "home".. The cows get bred and then they go visiting. Once they don't respect the fences, they leave. Sold one a couple of years ago because his attitude just bothered me. He wasn't really aggressive, but would snort at you and just watch you, and I never felt safe near him. We bought him with a group of cows and he was fully mature when we got him. He also had some feet issues. Yes, all bulls need to be respected and never "trust" them; but some just are "less trustworthy". I cannot run fast enough or climb a fence fast enough to get away from one that I don't feel at least comfortable to be around. Ours are all pretty quiet and calm, come to feed into the pens, and most will load up in the trailer with just a bucket of feed right out of the pasture. I worry more about a cow with a new calf than a bull most times. I have been hurt by cows with an over protective attitude with a new calf. And we don't keep cows that have an attitude anymore. I like protective, and will tolerate a cow that doesn't want me near her brand new baby, but will not tolerate one that wants to hurt me. These cows are used to me and have been worked around, they know I am not the enemy. Standoffish for a few days with a new calf is fine.
I also agree with snoopdog. 3 months is young, you can always make him a steer a little later on. A bull is half you calf crop, so a good one is very well worth spending a little money on.