There's an old joke about a young bull and an old bull on a hill looking at cows. The young bull says "Let's run down there and breed a cow!", the older bull says "No, let's walk down and breed them all".
This joke is based on observations that older bulls usually will only breed a cow once, they conserve their energy better than young bulls. Some young bulls will breed the same cow over and over being in such a state of arousal thet he doesn't breed another cow that is in heat right next to him.
Some young bulls are smart and some old bulls are stupid, but generally it's the other way.
Jason Trowbridge Southern Angus Farms Alberta Canada