Ah, my dear Jimmy, a sticky subject indeed for some, but not for me.
I used to do as you are doing, like clockwork, multiple animals as I
took in the unwanted, the homeless strays, etc.
THEN I got sick with autoimmune disease, like measles, they multiply.
Had to do research as I slowly learned the Dr's didn't know anything
and weren't helping me, in fact, got sicker!
What I learned changed how I thought and now, I do as your breeder
friends are doing because it's proven, ourselves & our animals are being
over vaccinated and that's very dangerous. Just as in humans, autoimmune
diseases are ever more dx'ed in animals and a big cause (I believe) is too
many vacs, given too often and many not needed.