Most vaccinated birds I have bought from big breeders are hopeless. Most die within a couple years and egg quality usually fails after a season or 2. Usually you get IB signs on the points of the eggs and then they stop laying. I'm not sure if this is down to the vaccination itself or the genetics of the parent stock. A big rearer was telling me the other day that all his light sussex (look like them anyway) come from Poland or Bulgaria and the parents are selected only to pass on sexing features in the feathers so that they can be sexed at hatch. They don't care about shell quality, laying ability, hardiness, foraging skills, not roosting in nest boxes etc.
I usually hatch from hens which have survived a couple molts and are still laying good strong and nicely shaped eggs. I want birds who are active, roost well, eat well and are out on the forage when possible. Also heavier birds so the cockerels make a good meal. Try to keep your growers on fresh grass where possible (we use Salatin style chicken tractors) and get them on grass as soon as possible.
I can't actually recall losing one of our own bred hens early.