I have to say i have never thought of anything other than getting the boosters - this thread is very interesting and will certainly make me think twice.
I have never heard of the testing for immunity but this seems like such a better option - then you are only getting done what is needed? Costs don't worry me to be honest I would rather pay for immunity and then a booster if required if it is better for the dog.

Do you get these tests done at the Vets and what is involved