From what I understand, if it's not a problem in your area, it's not likely that they will catch it. If the particular season is extra buggy, than perhaps look into it.
I don't breed, but planned on putting my dogs on heartworm medication. When I asked my vet she said there are so few cases in our area that it's not really neccessary, or in other words NOT giving it to them is not a big risk at all.
Same with flea medication. I had my guys on Advantix? I believe... I forget, last summer. And just never got around to it this year. No fleas!
They are outside a lot but I haven't seen any, and I check them regularly.
I think a lot of those medications/vaccinations aren't really neccessary.
I got the good lecture about over vaxing my animals, and now they will be getting their rabies only once every three years. When I mentioned it to my vet she aggreed whole heartedly. I asked her why than, do they send out notices every year to remind people to come in for rabies?!?
Her answer: With most people there's no other way I would see their dog. Otherwise I'd see their dog once every three years and that isn't enough. With people that I know, will bring their dog in for at least annual check ups, or if something seems wrong, I have no problems doing rabies once every three years. The shots good for that long so why not!?! LOL