Good point. Bulls probably are best judged at 14-18 months, because that is pretty close to where most calves get killed. Of course we measure the bull at birth to get an idea of what his calves will weigh at birth. We weigh the bull again at 205 days to get an idea what his calves will be like at weaning (market for most people). We weigh the bull again at 365 days to see what his calves will be like coming off of a stockering program. Ideally we then ultrasound several months later for carcass traits like REA, BF, and IMF and give him a breeding soundness exam to see that he checks out as a breeder. At 3 yo a bull is generally weighed and a final frame score is determined. This helps to produce an estimate of the progeny's mature frame and weight. A top herdsire prospect generally is visually evaluated at 205 days, 365 days, 18 months, 24 months, and at 36 months and increasingly, for a promoted bull, photos are taken at those steps.