Ya know... I hear a lot of people say you can't use a young bull on a lot of cows, but I have. The last bull I bought was a black Angus out of a red Angus cow, from a high powered breeder that only had the red cow because he had a kid that liked it and he gave it to the kid. One of the best looking Angus I've ever seen and I got him cheap because, of course, he was heterozygous. He was 18 months old and I put him on forty cows, and he settled them all. I don't know your situation but I'd look at the (long) yearlings with the idea that they will be older when I would be using them.