They are all pesticides (flea/tick and heartworm preventives) not medications.
I am in the same boat, lots of woods here. I use Advantix II every month, late spring-fall, Sentinel every 6 weeks May-November. Annual heartworm test.
I also use Preventic collars (amitraz) sometimes alone or in conjunction with topicals.
Some vets may say this is too much, some vets say it is okay, but to apply them at different times, I suspect the collar is only really good for a month anyway (not 3 months).
I also use homeopathic remedies such as Wondercide spray, brewers yeast tablets, a garlic clove about once a week….all controversial.
