Iam kind of on both sides of the fence on this. I give all my dogs their 9 in 1 shots. puppys 6,9,12,and 15weeks, and my grown dogs get one every spring until they are 5 years old. Ive never had any problems, but as stated, if I did i wouldnt have a leg to stand on as far as any litagation. Its a risk I choose to take. As far as heartworms and intestinal worms I bite the bullet and use Trifexis. 8 dogs equals about $125-$130 per month, or about $16 per dog. I know some sad stories with self administered Ivermectin in dogs, and thats a chance I choose not to take. All mine get an annual checkup at the vet after hunting season.
I dont think its anything wrong with doing things yourself to help your dog(s) (just like we dont take our kids to the doctor everytime they sneeze). I think knowing when to get your dog Professional care is imperative. Maybe our resident vet here can give us some more info on when we need to get our dogs to a Vet.