One of my hunting partners who has hunted for decades told me that you should always rotate your dogs out, keep them challenged this way and when something happens to your lead dog that cause it to be layed up you wont be up a creek with out a paddle and eventually something will happen that you have to lay up your lead dog for a while. I try to rotate my dogs for this reason alone.
I think that is some sound advice! Make those younger less experienced dogs produce. Let them know that if they dont find it nobody will. You will likely end up with more good dogs and not just one good one and some help dogs. I have seen dogs that hunt the lead dog hunted with other dogs and no lead dog and they will shine like new money, they knew they had to step up or go home empty handed!