Will Falconer, DVM Moderator
Some good ideas here. Key point is being on top of the situation, as you pointed out. Most vets know less than you about immunology, if you've been reading here for a while. We just weren't well schooled in it. Yearly repetition? If it's on the label, they'll do it!
And, Only for Use in The Healthy? Very narrowly defined, if at all. So, establishing this yourself ("Allergies mean unwell, do they not?") and getting it on the record will help your case. I wrote about this in my Vaccine Waiver page.
In the end, it's about taking the responsibility for your animal's health, as one with a vested interest. You're the best one, maybe the only one, to do this properly. Learn all you can and advocate for your animals.